Architectural Evolution of Stupas in the Western Regions During the Han and Tang Dynasties

Abstract

The Western Regions during the Han and Tang Dynasties served as a significant cultural intersection along the Silk Road, with stupas acting as core architectural forms of Buddhist dissemination, embodying religious, cultural, and artistic evolution. This study is a research article based on typological analysis, integrating historical documents and archaeological site data to explore the stylistic evolution of stupa architecture in the Western Regions during the Han and Tang Dynasties, revealing the changes in religious beliefs and the process of cultural adaptation and integration of Buddhism in a multicultural context. The study demonstrates that the distribution of stupas shifted from being concentrated in areas such as Shanshan and Shule during the Han Dynasty to expanding across a wider region during the Wei, Jin, and Northern and Southern Dynasties, eventually forming a Gaochang-centered pattern in the Tang Dynasty. Architectural styles evolved from the simplicity of domed stupas to diversification and then to standardization. The number of niches increased from none to many before decreasing again, while the proportions of the stupa bases gradually increased. This evolution highlights the transition of stupa styles from a singular form to diversification, eventually achieving standardization in the Tang Dynasty. This transformation not only reflects the optimization of the temple layout, gradually shifting from a stupa-centered to a Buddha hall-centered structure, but also illustrates the evolution of stupas from symbols of the Buddha’s tomb to carriers for Buddha statues and ultimately to representations of the Mount Sumeru cosmological concept. This transition also mirrors the shift in Buddhist beliefs, evolving from Theravāda to Mahāyāna Buddhism and then returning to Theravāda practices. This not only facilitated the regionalization of stupa forms and the integration of artistic styles but also provided a significant medium for cultural exchange between China and the West.

1. Introduction

The stupa, as a significant form of Buddhist architecture, originates from the tradition of enshrining the Buddha’s relics within a structure following his parinirvana. Its Sanskrit name, sthūpa, symbolizes the presence of the Buddha and serves as the central focus of devotion for followers [1]. Buddhist art in the Western Regions was profoundly influenced by the Gandharan style. By the Han and Tang Dynasties, stupa structures typically consisted of a pedestal, base, body, hemispherical dome, flat top, and finial.

However, over time, and due to the destruction caused by wars, most stupas now exist in a fragmented state, with the original forms of their pedestals, bases, and bodies often difficult to discern. This deterioration poses significant challenges for studying the complete architectural form of stupas. Traditional research methods, which rely on singular textual references or partial archaeological materials, struggle to comprehensively reveal the specific evolutionary patterns of stupa development.

Against this background, this study integrates typological analysis and archaeological data, focusing on stylistic forms and proportional relationships as primary entry points. The research examines the regional distribution and architectural evolution of stupas across different periods, with particular attention to changes in the proportions of bases and bodies as well as decorative styles. By conducting an in-depth analysis of these key elements, this study aims to reveal the significant role of stupas in cultural transmission and cross-cultural exchange.

1.1. Historical Background

The spatial scope of this study is limited to the Xinjiang Uyghur Autonomous Region of China, located in the central part of the Eurasian continent, in the northwest of China. It borders Gansu and Qinghai provinces to the east, and the Tibet Autonomous Region to the south. With a total area of 1.66 million square kilometers, Xinjiang is the largest provincial-level administrative region in China, accounting for approximately one-sixth of the country’s total land area.

This study focuses on the Han and Tang Dynasties, approximately spanning from the 2nd century BCE to the 10th century CE. Following Zhang Qian’s exploration of the Western Regions during the Western Han Dynasty, interactions between the Central Plains and the Western Regions grew increasingly frequent from the Han and Tang Dynasties, with the peak occurring during the Han and Tang periods. This study divides the timeline into three periods—the Han Dynasty (202 BCE–220 CE), the Wei, Jin, and Northern and Southern Dynasties (220–589 CE), and the Tang Dynasty (618–907 CE)—based on shifts in central authority and governance methods over the Western Regions. During these periods, the spread and reintroduction of Buddhism led to a gradual evolution in the stupa styles of the Western Regions.

Buddhism originated in ancient India in the 6th century BCE, founded by Siddhartha Gautama (Shakyamuni). Its philosophies and teachings rapidly spread throughout the Indian subcontinent. By the 3rd century BCE, Buddhism had reached its zenith during the reign of Emperor Ashoka of the Maurya Dynasty. With Ashoka’s support, Buddhism extended beyond India to other regions. During this period, Greek culture along the Mediterranean, introduced to the Indian subcontinent through Alexander the Great’s eastern conquests, infused Indian Buddhist art with the aesthetic principles of Greek sculpture. This cultural exchange gave rise to the Gandhara art style, which brought significant transformations to Buddhist architecture and sculpture.

By the 1st century CE, the Kushan Empire had emerged in South Asia. With the strong support of the Kushan rulers, Buddhist architecture experienced rapid development, and stupas became prominent as significant religious structures. During this period, the renowned Gandhara art of the Kushan era integrated elements of Greek, Persian, and indigenous Indian artistic traditions, enriching Buddhist architecture with intricate sculptural decorations and distinctive artistic styles.

Between the 1st and 5th centuries CE, Gandhara art spread to the Tarim Basin and regions further east through the extensive cultural influence of the Kushan Empire. The design and decoration of Buddhist temples and stupas in these areas were deeply influenced by Gandhara art, becoming a defining characteristic of the development of Buddhist architecture in the Western Regions.

According to scholar Li Taiyu, the early dissemination of Buddhist culture was initially concentrated around the Tarim Basin and the northern grassland areas, gradually extending to the Ferghana Valley and the Hexi Corridor. The Khotan region became the first entry point for Buddhism into China. While there is no consensus among scholars regarding the exact timing of Buddhism’s introduction, it is generally believed to have occurred between the 1st century BCE and the 1st century CE [2].

During this period, Buddhism not only spread its religious teachings but also introduced the stupa as a representative form of religious architecture to the Western Regions. Through continuous cultural exchanges, this contributed to the localization and development of Buddhist architecture in the region.

1.2. Introduction to Stupas

The stupa, originating in ancient India, is a significant symbol and architectural form in Buddhist culture. Initially, stupas were designed to enshrine the relics of Shakyamuni Buddha or to commemorate his nirvāṇa, serving as important sites for veneration and spiritual practice among followers. With their unique structure, stupas embody Buddhist religious philosophy. Their basic components typically include a base, a main body, a dome, and decorative elements on top, such as a parasol. As Buddhism spread, stupas evolved into various forms and became integrated with the architectural traditions and artistic styles of different regions.

The Western Regions were a key area for the eastward transmission of Buddhism. After Buddhism was introduced to this region between the 1st century BCE and the 1st century CE, stupa architecture gradually developed and became widely distributed. According to the existing historical records and archaeological remains, stupas in the Western Regions were primarily concentrated in the southern Tarim Basin and major cities south of the Tianshan Mountains, including Khotan (present-day Hotan), Kashgar, Shache, Aksu, and Kucha. These areas were not only critical hubs along the Silk Road but also centers for the dissemination of Buddhist culture and the fusion of architectural art.

According to Xuanzang’s records, the Khotan region was characterized by a strong emphasis on Mahayana Buddhism, as “many people practiced and studied the teachings of the Mahayana tradition” (多习学大乘法教) [3]. In contrast, Theravada Buddhism predominated in regions such as Kashgar, Shache, Aksu, and Kucha. The formation of this religious landscape is closely related to the historical context of Buddhism’s dissemination and the varying cultural receptivity of different regions. Chinese and Tibetan historical texts also document that as early as the 1st century CE, the Kashmiri monk Vimalakṣa (毗卢折那) was already propagating Buddhist teachings in Khotan, marking the beginning of Buddhism’s spread in northwestern China. These religious activities not only facilitated the dissemination of Buddhist faith but also contributed to the flourishing development of stupa architecture in the Western Regions.

The main objectives of this study include the following three points:

1. To analyze the evolutionary characteristics of stupa styles in the Western Regions during the Han and Tang Dynasties from a typological perspective.

2. To analyze the geographical and temporal characteristics in the evolution of stupas.

3. To explore the influence of cultural exchanges on the formation of stupa architectural styles and their development.

1.3. Literature Review

1.3.1. Archaeological Excavation Report

From the late 19th to the early 20th century, explorers such as Sven Hedin and Aurel Stein conducted a series of archaeological excavations in Xinjiang, uncovering and documenting significant sites like Niya and Loulan. Stein’s works, Ancient Khotan [4] and Serindia [5], and Hedin’s Through Asia [6], provide detailed descriptions of the sites in the Tarim Basin, offering invaluable resources for the study of stupas in the Western Regions. Between 1902 and 1903, Albert Grünwedel and Albert von Le Coq excavated numerous Buddhist structures, murals, and sculptures in the Turpan Basin, publishing their findings in Archaeological Report on Gaochang and its Surroundings: Winter 1902–1903 [7]. From 1902 to 1914, the Japanese Ōtani Expedition, led by Count Ōtani Kōzui, conducted three expeditions in Xinjiang, compiling their findings into the Illustrated Archaeological Atlas of the Western Regions [8]. Between 1908 and 1909, French archaeologist Paul Pelliot explored sites in the Kashgar and Kuqa oases, documenting his findings on Buddhist remains in Notes on Pelliot’s Expedition to the Western Regions [9]. From 1909 to 1910, Russian scholar Sergei Oldenburg surveyed sites in Yanqi and Turpan, preserving murals and Buddhist relics. His findings were later compiled into the Preliminary Report of the Russian Expedition to Xinjiang, 1909–1910 [10].

Chinese archaeological research in the Western Regions began in 1915, with Lin Jing conducting investigations in various locations across Xinjiang. In 1928, Huang Wenbi participated in the Sino–Swedish Northwest Scientific Expedition and conducted systematic studies of Buddhist sites in the Western Regions. His monumental works, Archaeological Report on Turpan [11] and Archaeological Report on the Tarim Basin [12], meticulously documented detailed data on the plans and forms of stupas across different regions of Xinjiang.

From 1988 to 1997, the Sino–Japanese Niya Site Expedition conducted eight comprehensive surveys and excavations of the Niya site. Findings related to stupas and associated relics were published in the Sino–Japanese Joint Academic Investigation Report on the Niya Site [13], providing critical insights into the dissemination pathways of Buddhism in the Tarim Basin.

Additionally, between 2007 and 2011, the Xinjiang Weiwuer Autonomous Region Bureau of Cultural Relics organized a comprehensive cultural relics survey, with the findings compiled into Immovable Cultural Heritage [14] (30 volumes) and Compilation of Results from the Third National Cultural Relics Census of Xinjiang Uyghur Autonomous Region [15] (28 volumes). These works include detailed investigations and records of stupas and their sites. In particular, the volume Xinjiang Buddhist Sites: Results of the Third National Cultural Relics Census of Xinjiang Uyghur Autonomous Region [16] systematically summarizes the survey results of stupa architecture, serving as a fundamental reference for the study of stupas and culture in the Western Regions.

In recent years, significant progress has been made in the archaeological excavations of the Subashi Buddhist Temple and Mor Temple. Excavations at the Mor Temple from 2019 to 2021 revealed its architectural layout and religious functions, with Findings from the Excavation of the Kashgar Mo’er Temple Site in Xinjiang, 2019–2021 [17] and Buddhist Archaeology in Xinjiang: Discoveries and Significance of the Mor Temple Excavation [18].

In early 2021, Professor Zhou Xiaodi’s team from Southeast University conducted mapping and scanning of the Subashi Buddhist Temple site. Related archaeological findings were included in the appendix of A Study on the Architectural Form of the Subashi Buddhist Temple in Xinjiang [19], laying a foundation for further research on Buddhist architecture in the Western Regions.

1.3.2. Studies on Stupas

The classification and development patterns of stupas in the Western Regions have been explored to some extent in academic research. The existing literature primarily focuses on typological studies, cultural exchange and localization, as well as the relationship between stupas and temple layouts.

In terms of typology, Song Lizi classified stupas into categories such as stupa type, square tower, stupa temple type, the Milan M.II representative type, and octagonal columnar tower, providing a foundation for the classification used in this study [20]. Lin Li focused on the Gaochang region, analyzing the evolution of stupas and central pillar towers, highlighting patterns in the number of stupa tiers and niches [1]. Ziyun, Zeng, and Xiaodong, Wang further summarized stupa types in the southern and northern edges of the Tarim Basin and the eastern Tianshan region, analyzing features of cross-shaped plan stupas, high-platform stupas, and hemispherical domed stupas, revealing their diversity and regional characteristics [21]. However, these studies have not thoroughly examined the evolutionary logic between types or established a detailed chronological sequence.

In the realm of cultural exchange and localization, Kim, Y. J. analyzed the transformation of Buddhist architecture from Indian stupas to East Asian pagodas, revealing the transmission and adaptation of terminology, functions, and forms [22]. While this study provides theoretical support for understanding the cultural transformation of stupas, it falls short in addressing the specific architectural practices of the Tarim Basin.

Research on the relationship between stupas and temple layouts has also made some progress. Nakamura Yuka and Okazaki Jinsei classified 55 Buddhist temples in Central Asia into four types of shrine buildings and examined the influence of worship practices on spatial layouts [23]. Later, Nakamura and Okazaki proposed a spatial classification of stupa courts and their association with worship behavior [24]. Li and Liao, through a comparative study of Gandharan and Tarim Basin temple layouts, uncovered spatial pattern changes under the influence of cultural integration [25].

In summary, the existing research provides important references for understanding the stylistic types and development patterns of stupas in the Western Regions during the Han and Tang Dynasties. However, gaps remain in the analysis of chronological sequences, the evolutionary logic between types, and the interaction between regional characteristics and cultural dissemination. Building on typological studies and integrating specific site and architectural data, this study aims to further explore the architectural development patterns and cultural significance of stupas in the Tarim Basin.

1.4. Structure of the Paper

This paper follows a standard academic structure and focuses on the study of Buddhist stupa architecture in the Western Regions during the Han and Tang Dynasties. The paper is divided into the following sections (Figure 1):

Section 1 of this paper comprises the introduction, which includes the research background, research questions and objectives, and a literature review. Its purpose is to clarify the academic value and research direction of this study while providing an overview of the logical framework of the paper.

Section 2 covers the research methodology and data sources, detailing the methods employed in the study, including the analysis of geographical distribution and chronological framework, as well as the selection and integration of data sources, which provide theoretical and data support for the subsequent analysis.

Section 3 presents the results, analyzing the regional distribution, chronological span, stylistic features, and proportional relationships of the studied objects. It summarizes the evolution characteristics of Buddhist stupa architecture in the Western Regions across different periods.

Section 4 is the discussion, which, based on the results, explores the evolutionary trends of Western Region stupas in terms of time and geographical distribution, analyzes the development patterns of their styles, and focuses on the changes in stupa proportions and their symbolic significance.

Section 5 is the conclusion, which summarizes the main findings of this research, consolidates the key evolutionary patterns of stupa architecture, and offers insights for future research.

2. Methods and Data Sources

2.1. Methods

This study employs a combination of typological analysis, statistical methods, and comparative analysis, along with data organization and visualization techniques, to systematically analyze the geographical distribution and stylistic characteristics of, and proportional changes in Buddhist stupas in Xinjiang during the Han and Tang Dynasties. The research process is divided into the following stages:

2.1.1. Literature Review and Data Organization

This study utilized the literature analysis method to extract stupa data from domestic and international archaeological findings. The data were classified and recorded based on dimensions such as “Type”, “Period”, “Region”, “Shape of Stupa Base Plan”, “Niche Arrangement”, “Corbeling Structure”, and “Relief Decorations”, forming a stupa instance database. During data organization, Excel (version 16.78.3 (23102801)) was used for sorting and categorization, ensuring data consistency and completeness.

2.1.2. Typological Analysis Method

Typological analysis was employed to summarize the structural features of stupa architecture, aiming to uncover patterns of evolution and regional characteristics. The classification criteria focused on four primary dimensions: plan shape, niche arrangement, corbeling structure, and relief decorations.

Stupas were categorized temporally into the Han Dynasty, Wei, Jin, and Northern and Southern Dynasties, and Tang Dynasty, and geographically into eight regions: Shule, Shache, Khotan, Kuqa, Yanqi, Gaochang, Shanshan, and Yiwu. Plan shapes included square, circular, cross-shaped, and polygonal forms, with data primarily sourced from archaeological reports, including plans and textual descriptions, supplemented by early survey drawings in the historical literature. Niche arrangements were classified by number and location, including no niches, single niche on the front, one niche on each of the four sides, and multiple niches on all four sides. Corbeling structures and relief decorations were categorized based on their presence or absence. This typological analysis clarifies the fundamental classification standards of stupa architecture, providing theoretical support for subsequent statistical and comparative studies.

2.1.3. Statistical Analysis

Statistical analysis employs quantitative methods to reveal the geographical distribution, temporal evolution, and stylistic characteristics of stupas. This study used Excel to classify and calculate the instance data. First, frequency statistics were conducted to quantify the number of stupas of different types across various periods and regions, uncovering patterns in their temporal and spatial distribution. Second, proportional analysis was performed on stupa plan shapes and decorative features, calculating the percentage of each type across different time periods and presenting the results through charts to illustrate proportional relationships.

Trend analysis was also applied, using line graphs to visualize changes in stupa quantities over time, with a focus on highlighting the rise and decline of each type. These statistical methods not only reveal the evolutionary patterns of architectural styles but also provide foundational data for subsequent stylistic summarization and comparative analysis.

2.1.4. Diagrammatic Analysis and Visualization

Based on the results of the statistical analysis, AutoCAD software 2018 (version 0.49.0.0) was used to create plans and elevation drawings of representative stupa examples, which were further refined using Photoshop for enhanced detail. These diagrams visually present the key architectural features of stupas, supporting the conclusions of the typological and comparative analyses while providing an essential visual foundation for the research.

2.1.5. Comparative Analysis and Synthesis

Building on the results of the statistical and diagrammatic analyses, the comparative analysis method was employed to examine the structural and stylistic features of stupas across different regions and time periods. This approach explores the influence of cultural exchange on architectural styles. Through comparative analysis, the study synthesizes the evolutionary patterns of architectural styles and proportional changes, further elucidating the cultural significance of stupa styles in the Western Regions during the Han and Tang Dynasties, with insights supported by the historical literature.

2.2. Data Sources

The data used in this study primarily rely on domestic and international literature and archaeological materials, which provide rich case data and a reliable analytical foundation. The time frame is limited to the Han and Tang Dynasties, a period that marks the peak of Buddhism’s spread in the Western Regions and a key stage in the development and transformation of stupa architectural styles. The geographical scope of this study is limited to the modern Xinjiang region, aiming to analyze the stylistic characteristics and evolutionary patterns of Buddhist stupas in this area and explore how stupa architecture reflects the cultural exchange between the Central Plains and the Western Regions along the Silk Road. During the Han and Tang periods, the central areas of the historical Western Regions were largely located within the boundaries of modern Xinjiang. Furthermore, the existing archaeological and historical data are predominantly concentrated in this region, enabling the research to be conducted based on reliable site data. In terms of content completeness, priority was given to selecting literature that included case data, physical photographs, and detailed excavation records to ensure the systematic nature of the research and the reliability of the data. Some sites, due to incomplete morphological characteristics, were only used for analyzing geographical spatial distribution and were not included in the typological classification. The selected research objects are shown in

Table 1. Selected research objects.

No.	Type	Period	Region	Name	Plan	Niches	Corbeling	Relief Decorations
1	A	2nd–3rd C.	Shanshan	Miran M.XIV Stupa	I	I	I	II
2	B-1	2nd–3rd C. [26]	Shanshan	Miran M.III Stupa	II	I	I	II
3	B-2	2nd–3rd C. [26]	Shanshan	Miran M.V Stupa	II	I	I	II
4	Ca-1	2nd–10th C.	Khotan	Andir No. 1 Stupa	III	I	II	II
5	Ca-2	Late 3rd C. AD [26]	Shanshan	Loulan LA.X Stupa	III	I	I	II
6	Ca-3	Late 3rd C. AD [26]	Shanshan	Loulan LA.XI Stupa	III	I	II	II
7	Da	2nd–4th C.	Quli	Yingpan Buddhist Temple Stupa/ Stein I.i Buddhist Temple Stupa	IV	I	II	II
8	Ca-2	Late 3rd C. AD [26]	Khotan	Niya Stupa	III	I	II	II
9	Ca-3	Late 3rd C. AD [18]	Shule	Mo ’er Temple	III	I	II	II
10	Dd-1	3rd–7th C.	Kuqa	SE2-4 P1 Stupa in the East Temple of Subashi Buddhist Temple	IV	II	II	II
11	Cc	3rd–7th C.	Kuqa	SW3-2 Site of the West Temple in Subashi Buddhist Temple	III	II	II	II
12	Dd-1	3rd–7th C.	Kuqa	P1 Stupa in the Main Hall of SW2-2 West Temple, Subashi Buddhist Temple	IV	II	II	II
13	Dd-2	3rd–7th C.	Kuqa	P1 Stupa at the SW4-4 Site of the West Temple, Subashi Buddhist Temple	IV	II	I	II
14	Cd-2	3rd–7th C.	Kuqa	Stupa in Cave 18 of the Tohurak Aiken Grottoes	III	IV	II	II
15	Cd-1	5th–14th C.	Gaochang	Taizang Stupa	III	IV	II	II
16	F	4th–5th C. [27]	Gaochang	Main Stupa of Pagoda Forest E-17 in the Ancient City of Jiaohe	VI	IV	I	II
17	Ce-2	4th–11th C.	Gaochang	Small Stupa in Front of the Main Stupa of Pagoda Forest E-17 in the Ancient City of Jiaohe	III	III	I	II
18	Cc	7th–11th C.	Yiwu	Miaergou Stupa F1	III	II	II	II
19	Df	4th–11th C.	Gaochang	Stupa of the Great Buddhist Temple in the Ancient City of Jiaohe	IV	IV	II	II
20	Dc	4th–5th C. [27]	Gaochang	Stupa E-13-1 in the Ancient City of Jiaohe	IV	III	II	II
21	Dd-1	AD 327–640	Gaochang	Stupa in Cave 36 of the Tuyugou Grottoes	IV	II	I	II
22	G	5th–10th C.	Khotan	Rewak Buddhist Temple	VII	I	II	II
23	Cb-1	4th–6th C. [17]	Shule	Mor Temple No. 2 Stupa	III	IV	II	II
24	Cc	7th–8th C. [27]	Gaochang	Central Stupa E-28 in the Ancient City of Jiaohe	III	II	II	II
25	De	7th–10th C.	Yiwu	Xiaonanhu Stupa	IV	II	I	II
26	Cb-2	7th–14th C.	Gaochang	Site Y in the Ancient City of Gaochang	III	IV	II	II
27	Dd-2	Early 5th C. [28]	Gaochang	Stupa in γ Buddhist Temple, Ancient City of Gaochang	IV	I	I	II
28	Df	6th–8th C. [28]	Gaochang	Central Stupa of β-A Buddha Hall in the Ancient City of Gaochang	IV	IV	II	II
29	Dg-2	6th–8th C. [28]	Gaochang	π Buddhist Temple Stupa in the Ancient City of Gaochang	IV	I	II	II
30	Df	6th–8th C. [28]	Gaochang	W Buddhist Temple Stupa Column in the Ancient City of Gaochang	IV	IV	II	II
31	Df	6th–8th C. [28]	Gaochang	ρ Buddhist Temple Stupa in the Ancient City of Gaochang	IV	IV	I	II
32	Ce-1	7th–14th C.	Gaochang	Small Stupa of P Pagoda Forest in the Ancient City of Gaochang	III	III	I	II
33	F	7th–14th C.	Gaochang	Central Stupa of P Pagoda Forest in the Ancient City of Gaochang	VI	III	II	II
34	Dg-1	7th–14th C.	Gaochang	y Stupa in the Northern Great Pagoda Group of the Ancient City of Gaochang	IV	II	I	I
35	Dd-2	7th–14th C.	Gaochang	Stupa in the Northern Great Pagoda Group of the Ancient City of Gaochang	IV	IV	I	II
36	Ea	7th–14th C.	Gaochang	Unnamed Stupa in the Ancient City of Gaochang	V	II	II	II
37	Eb? 1	7th–14th C.	Gaochang	South Stupa D of II Buddhist Temple in the Ancient City of Gaochang	V	I	II	II
38	H-1	7th–10th C.	Quli	Yingpan II Stupa	VIII	I	II	II
39	Cd-2	7th–10th C.	Shanshan	Srkov Stupa	III	IV	II	II
40	Dg-3	7th–13th C.	Yanqi	Seven-Star Stupa D2	IV	I	I	I
41	Db	7th–13th C.	Yanqi	Seven-Star Stupa C3β	IV	II	II	II
42	Eb	7th–13th C.	Yanqi	Seven-Star Stupa D5	V	II	II	II
43	Eb	7th–13th C.	Yanqi	Seven-Star Stupa C2	V	II	II	II
44	H-2	5th	Shanshan	Miran M. II Buddhist Temple	VIII	IV	II	I

Note: The period data not marked are sourced from [15]. ¹ The base is severely collapsed, and based on a hole on the body of the stupa, it is speculated that it might be of the Eb type.

.

The data were primarily sourced from the literature mentioned in the literature review section, including Xinjiang Buddhist Sites: Results of the Third National Cultural Relics Census of Xinjiang Uyghur Autonomous Region [15] and Immovable Cultural Heritage [14], among others. For sites with poor preservation, early records and photographs by foreign scholars were referenced, providing valuable insights into the original forms of collapsed sites. These sources offer abundant case data and a reliable foundation for analysis in this study.

Additionally, these bibliographic materials were integrated into a case database. The classification criteria (

Table 2. Classification table of architectural elements and types of Han and Tang Buddhist stupas in the Western Regions (drawn by the authors).

Niche
	I	II	III	IV
	No niche	One niche on the front	One niche on each of the four sides	Multiple niches on each of the four sides
Corbeling
	I	II
	With tiered structure	Without tiered structure
Decorative Reliefs	[29]	[7]
	I	II
	With decorative reliefs	Without decorative reliefs
Plan
	I	II	III	IV
	V	VI	VII	VIII

) include type (classified based on the architectural features of the stupas), period (indicating the construction period of the stupa), region (recording the geographical location of the stupa), plan shape (the plan form of the stupa, such as square, circular, cruciform), niches (statistics on whether niches are present and their distribution forms), stepped structure (whether a stepped structure is used), and decorative reliefs (whether decorative reliefs are present, excluding stepped structures). These data were entered, classified, and statistically analyzed using Excel (version 16.78.3 (23102801)), providing significant support for subsequent research on geographical distribution, stylistic features, and proportional analysis.

The classification of periods in this study was primarily based on the founding time of the sites, dividing them into three historical stages: the Han Dynasty, the Wei, Jin, and Southern and Northern Dynasties, and the Tang Dynasty. The period data were mainly sourced from Xinjiang Buddhist Sites: Results of the Third National Cultural Relics Census of Xinjiang Uyghur Autonomous Region [15], with data from other sources separately marked in the table.

The typological classification criteria are primarily based on the shape of the stupa base’s ground plan, the number and location of niches, the presence or absence of corbelling and decorations, and the number of tiers of the stupa base.

3. Results

3.1. Temporal and Regional Distribution Analysis

This study utilized statistical data from existing stupa remains to infer the distribution of stupas across different times and regions. Our analysis is based on the assumption that although the existing remains may only represent a portion of all of the stupas, historically, their distribution across time and space can reflect certain historical patterns and cultural trends. We believe that, despite the possibility that some stupas may not be included in the statistics due to differing preservation conditions, the widely distributed sample of remains provides valuable insights for our research.

Based on the data distribution (Figure 2), approximately 103 stupa remains from the Han and Tang Dynasties have been identified in the Western Regions. These remains are primarily distributed across Gaochang, Kuqa, Quli, Shache, Shanshan, Shule, Yanqi, Yiwu, and Khotan. Among them, Gaochang has the highest number of stupas, accounting for about 40.78% (42 sites), followed by the Shanshan region, which accounts for 15.53% (16 sites).

Referring to the statistical data shown in Figure 3, stupa remains from the Wei, Jin, and Northern and Southern Dynasties constitute the largest proportion of Buddhist sites in the Western Regions during the Han and Tang Dynasties, accounting for 46.60% (48 sites). Tang Dynasty remains rank second, making up 34.95% (36 sites), while Han Dynasty remains are relatively fewer, at 18.45% (19 sites). The distribution of these remains by their founding periods indicates that the Wei, Jin, and Northern and Southern Dynasties represented the peak of Buddhist architectural development, with significantly more sites compared to the Han and Tang Dynasties.

Drawing on the data distribution presented in Figure 4 and Figure 5, stupa remains from the Han Dynasty were primarily concentrated in Shanshan (6 sites), Khotan (6 sites), and Quli (5 sites), accounting for 31.58%, 31.58%, and 26.32% of the total Han Dynasty stupas, respectively. These sites were relatively concentrated. Additionally, stupas were also found in the Shule region. However, no stupa remains have been discovered in other regions, such as Gaochang, Kuqa, Yanqi, and Yiwu.

During the Wei, Jin, and Northern and Southern Dynasties, stupa remains reached a historical peak, with a much broader distribution, mainly concentrated in Shanshan, Gaochang, and Kuqa. Gaochang had the highest number of stupas, totaling twenty sites and accounting for 41.67% of the total. Kuqa began to see stupa construction, with ten sites accounting for 20.83%. Shanshan had nine stupa sites, accounting for 18.75%, while Khotan had five sites, representing 10.42%. The number of stupa remains in other regions was relatively small. The extensive expansion of stupas during this period nearly covered the entire Western Regions, marking a rapid spread of Buddhism.

In the Tang Dynasty, Gaochang remained the center of stupa construction, with twenty-two stupa sites, accounting for 61.11% of the total. Other regions also experienced some stupa construction, but the numbers were relatively lower.

According to Figure 6, the overall distribution of stupa types exhibits a noticeable imbalance. Among these stupa types, Type C and Type D stupas are the most prevalent, with 15 and 17 instances, respectively. Of all the stupa types, Type Dd stupas are the most common, with six instances, followed by Type Ca stupas, which have five instances.

As shown in Figure 7, the overall distribution of stupa types exhibits significant regional differences. Gaochang has the highest diversity, encompassing ten types of stupas, followed by Shanshan with five types. Among them, Type Ca stupas are more widely distributed, primarily concentrated in Gaochang, Shanshan, and Yanqi. Type Cc stupas appear in Gaochang, Kucha, and Yiwu, while Type Cd stupas are found in Gaochang, Kucha, and Shanshan. In contrast, certain stupa types have a more restricted distribution. Type A and Type B stupas are exclusively found in Shanshan, while Type Ce, Type Dc, Type Df, and Type F stupas are recorded only in Gaochang. Type Db and Type Eb stupas are limited to Yanqi, whereas Type G stupas are found solely in Khotan. Additionally, Type Da stupas are exclusively present in Quli.

The distribution of stupa types across different historical periods demonstrates significant variation, as shown in Figure 8. The Han Dynasty recorded the fewest stupa types, with only three identified, whereas both the Wei, Jin, and Northern and Southern Dynasties and the Tang Dynasty exhibited a greater diversity, each featuring ten types. Certain stupa types were exclusive to specific periods. For example, Type A, Type B, and Type Da stupas appeared only in the Han Dynasty. Type Ca, Type Dc, Type Df, and Type G stupas were limited to the Wei, Jin, and Northern and Southern Dynasties, while Type Db, Type De, Type Ea, and Type Eb stupas were recorded exclusively in the Tang Dynasty, without occurrences in other periods. The Wei, Jin, and Northern and Southern Dynasties exhibited a particularly high diversity of stupa types, some of which continued into the Tang Dynasty. Specifically, Type Cb, Type Cc, Type Cd, Type Ce, Type Dd, Type Dg, Type F, and Type H stupas were present in both periods, indicating a degree of architectural continuity.

This section primarily analyzes the temporal and regional distribution of stupas during the Han and Tang Dynasties, revealing that the Wei, Jin, and Northern and Southern Dynasties marked the peak of stupa construction with a significantly expanded distribution, centered around Gaochang. The Wei, Jin, and Northern and Southern Dynasties exhibited the greatest diversity of stupa types, with some continuing into the Tang Dynasty. However, the existing stupa remains may not fully reflect the actual historical distribution of all stupas, primarily due to the limited scope of archaeological excavations. Some sites may still remain undiscovered, or their preservation conditions may be poor. Therefore, the conclusions of this study, based on currently available data, have certain limitations, and future archaeological discoveries may further enrich and refine the understanding of their temporal and regional distribution.

3.2. Analysis of Stupa Architectural Features

Stupa bases and enclosures evolved significantly across periods (

Table 3. Statistical chart of architectural features in Buddhist stupas by period (drawn by the authors).

	Plan	Niches	Corbeling	Relief Decorations
Han Dynasty	I, II, IV	I	I, II	II
Wei, Jin, and Northern and Southern Dynasties	III, IV, V, VI, VII, VIII	II, III, IV	I, II	II
Tang Dynasty	III, IV, V, VI, VIII	I, II, III, IV	I, II	I, II

). Han Dynasty stupas primarily featured circular bases (Type I, II) and square bases (Type IV) with circular or square enclosures, continuing Gandharan traditions. During the Wei, Jin, and Northern and Southern Dynasties, circular bases (Type I) disappeared, while multi-tiered square (Type III), square (Type IV, V), octagonal (Type VI), Vajrasana-style (Type VII), and cruciform (Type VIII) bases emerged. Enclosure types expanded, introducing rectangular enclosures (Type V) alongside existing square forms (Type II, IV, VI, VIII). The Tang Dynasty retained multi-tiered square (Type III), square (Type IV, V), octagonal (Type VI), and Vajrasana-style (Type VII) bases, with square enclosures (Type IV, VI) becoming dominant, reflecting structural standardization. Overall, the Wei, Jin, and Northern and Southern Dynasties marked the peak of diversity, while the Tang Dynasty refined and standardized these forms.

In terms of niches, Han Dynasty stupas typically had no niches (Type I), resulting in a relatively simple architectural form. During the Wei, Jin, and Northern and Southern Dynasties, niche designs became more diverse. While the no-niche type (Type I) continued to exist, new forms emerged, including single-front niches (Type II), one niche on each of the four sides (Type III), and multiple niches on all four sides (Type IV). This evolution reflects the expansion of worship spaces and the increasing complexity of stupa architecture. The Tang Dynasty carried forward these developments, maintaining the established niche variations from the previous period.

Corbeling structures remained consistent across all periods, with both corbeling (Type I) and non-corbeling (Type II) coexisting.

Regarding relief decorations, Han Dynasty stupas were plain, with no decorations (Type II). The Tang Dynasty introduced relief decorations (Type I), resulting in the coexistence of both decorated and undecorated styles, highlighting greater diversity in artistic designs.

This section primarily analyzes the evolution of stupa architectural features, revealing that the Wei, Jin, and Northern and Southern Dynasties introduced new base shapes, niche types, and relief decorations, showcasing significant diversification, while the Tang Dynasty continued these styles.

3.3. Typological Analysis

As shown in Figure 9, the architectural forms of stupas underwent significant transformations across different periods. During the Han Dynasty, stupa types were relatively limited, primarily consisting of Type A and Type B, with Type B further subdivided into B-1 and B-2. While the superstructure of Type A stupas has not been preserved, the plan suggests that they featured a circular base and circular enclosure, forming an ambulatory. Type B stupas evolved from Type A, retaining the circular base and ambulatory, but the outer wall transitioned into a square enclosure. By the late 3rd century, the number of stepped layers increased, leading to the development of Type Ca. Stupas from this period did not include niches, and Type C stupas were enclosed by a square ambulatory, forming either a square or rectangular plan, which subsequently evolved into Type D.

The Wei, Jin, and Northern and Southern Dynasties marked the peak of stupa construction. Stupas from this period not only retained certain elements of Han Dynasty styles but also introduced a broader range of architectural forms. Type A and Type B stupas disappeared, while Type C further diversified. Type Ce developed from Type Ca with the addition of a niche on the front of the base and multiple stepped moldings to represent eave-like projections, resembling the multi-story pagodas of the Central Plains. Type D evolved by increasing both the number of tiers and the inclusion of niches, giving rise to Types Da, Dc, Dd, and De. Type Dc featured niches on all four sides of a two-tiered base, Type Dd had a single niche on the front, while Type De incorporated niches on every tier. Additionally, new types emerged, such as Type F (cross-shaped stupas), Type G (Vajrasana-style stupas), and Type H. Overall, this period witnessed a remarkable diversification of stupa forms, with increasingly complex structures and refined decorative techniques. The increase in stupa tiers became a key design feature, and niche arrangements varied widely. While most stupas had either a single niche on the front or niches on all four sides, stupas without niches largely disappeared.

During the Tang Dynasty, stupa forms largely inherited the fundamental types established during the Wei, Jin, and Northern and Southern Dynasties, with modifications and refinements. In the early Tang period, the number of niches significantly increased, giving rise to Types Cb, Cd, and Df, which featured multiple niches. The stupa body of multi-tiered bases transformed into a worship hall, leading to the emergence of Type Cc (high-platform stupa halls). However, by the 8th century, the number of niches was greatly reduced, and stupas without niches reappeared, while geometric decorative patterns became prevalent, marking a stylistic shift from earlier traditions. Tang Dynasty stupas achieved a balance between functionality and aesthetics, and their forms became increasingly standardized, following a developmental trajectory from simplicity to complexity, and then back to simplicity.

The evolution of stupa forms thus reflects a process of gradual transformation from the simplicity of the Han Dynasty to the diversification and complexity of the Wei, Jin, and Northern and Southern Dynasties, ultimately reaching a high degree of standardization in the Tang Dynasty.

3.4. Proportional Analysis

Table 4. Proportions of base height-to-width and kumbha-to-base ratios in stupa types across historical periods (drawn by the authors).

	Type	Han Dynasty	Wei, Jin, and Northern and Southern Dynasties	Tang Dynasty
Base Height-to-Width Ratio	A	1:3	None	None
	B	1:3	None	None
	C	1:2	2:1	1:2(Cb) 1:1(Cc) Greater than 1:1(Cd)
	D	1:2	1.5:1(Dc) 2:1(Dd, De)	2:1(Df) 1:2(Db)
E	E	None	None	1:2
Height Ratio of Kumbha to Base	A	None	None	None
	B	2:1	None	None
	C	1.5:1(Ca-1, Ca-2) 1:1(Ca-3)	1:2	None
	D	1.5:1	None	1:1(Db) None(Df)
	E	None	None	1:1

illustrates two primary trends in the base height-to-width ratio of stupas across different historical periods: proportion maintenance and proportion increase. In the Han Dynasty, Type A and Type B stupas both had a base ratio of 1:3, but they did not continue into later periods. Type C stupas initially had a 1:2 ratio, which increased to 2:1 during the Wei, Jin, and Northern and Southern Dynasties. By the Tang Dynasty, the proportions varied, with Type Cb at 1:2, Type Cc at 1:1, and Type Cd exceeding 1:1. Type D stupas, originally 1:2 in the Han Dynasty, evolved to 1.5:1 in Type Dc and 2:1 in Type Dd and Type De during the Wei, Jin, and Northern and Southern Dynasties. In the Tang Dynasty, Type Df maintained the 2:1 ratio, whereas Type Db decreased to 1:2. Type E stupas, which emerged in the Tang Dynasty, had a base ratio of 1:2. These shifts indicate a gradual structural transition, with Tang Dynasty stupas placing greater emphasis on the base rather than the kumbha, resulting in enhanced stability.

The height ratio of the kumbha-shaped top to the base shows a general trend of reduction over time. In the Han Dynasty, Type B stupas featured a 2:1 kumbha-to-base ratio. Among Type C stupas, Ca-1 and Ca-2 had a ratio of 1.5:1, while Ca-3 was 1:1. This ratio declined to 1:2 in the Wei, Jin, and Northern and Southern Dynasties, and no evidence of the kumbha remains in the Tang Dynasty. Type D stupas had a kumbha-to-base ratio of 1.5:1 in the Han Dynasty, which dropped to 1:1 in Type Db during the Tang Dynasty, while Type Df lacked a kumbha entirely. Type E stupas, appearing only in the Tang Dynasty, had a kumbha-to-base ratio of 1:1. Overall, the prominence of the kumbha diminished over time and ultimately disappeared in the Tang Dynasty, reflecting architectural refinements and functional transformations in stupa design.

3.5. Summary of Results

This section provides a comprehensive summary of the temporal and regional distribution, architectural elements, stylistic characteristics, and proportions of stupas during the Han and Tang Dynasties. The Wei, Jin, and Northern and Southern Dynasties marked the peak of stupa construction, with a significantly expanded regional distribution centered around Gaochang.

Stupa architectural features underwent significant evolution during the Wei, Jin, and Northern and Southern Dynasties, introducing new base shapes, niche arrangements, and relief decorations. The Tang Dynasty continued these styles with further refinements.

The design of stupas transitioned from the simplicity of the Han Dynasty to the diverse and intricate styles of the Wei, Jin, and Northern and Southern Dynasties, ultimately achieving a high degree of standardization during the Tang Dynasty.

Stupa design exhibited two main trends: the maintenance of or increase in base proportions and a shift in prominence from the kumbha to taller, layered bases.

4. Discussion

4.1. The Historical Evolution and Cultural Significance of Stupa Distribution

During different historical periods, the quantity and distribution of stupas reflected evolutionary patterns closely tied to political and cultural factors.

During the Han Dynasty, Buddhism was in its early stages of dissemination, resulting in a limited number of stupas with a relatively narrow distribution. At this time, Buddhism had not yet fully integrated into local culture, and its spread relied heavily on the geographical advantages of transportation hubs and limited regional political support. Shanshan and Khotan became the primary areas for stupa distribution: Shanshan, situated at the intersection of the Central Plains and the Western Regions, served as a center for the early spread of Buddhism, while Khotan, connected to the Indian subcontinent via the southern route, functioned as a crucial hub for the transmission of Buddhist scriptures and art. Additionally, the Shule region, located at the cultural crossroads of the Tarim Basin and the Pamir Plateau, also played an important role in the early dissemination of Buddhism.

During the Wei, Jin, and Northern and Southern Dynasties, a period considered the zenith of Buddhism’s development, societal turbulence and political instability provided significant opportunities for the spread of Buddhism. As a foreign religious tradition, Buddhism not only offered spiritual solace to the populace but was also regarded by rulers as a vital tool for consolidating power. Under the dual support of political and cultural forces, stupa construction entered a phase of rapid expansion. The focus of Buddhist dissemination gradually shifted from Shanshan and Khotan to Gaochang and Kuqa. Gaochang, as a crucial node on the Silk Road, developed into a core hub of Buddhist culture during this period, with a significant increase in the number of stupas. Meanwhile, stupa construction in Shanshan and Khotan also maintained a relatively high level due to continued political support. As Buddhism spread further across the Western Regions, the distribution of stupas extended to a broader range of areas, reflecting deepening cultural integration and the increasing functional diversity of Buddhist architecture.

The Tang Dynasty marked a mature stage of Buddhist development, with Buddhist architecture reaching a high standard overall. Stupas were widely present across the Western Regions, but their numbers in Gaochang were significantly higher than in other areas. Gaochang continued to serve as a core hub for Buddhist dissemination, with the number of stupas steadily increasing. However, compared to the Wei, Jin, and Northern and Southern Dynasties, the number of stupas in Shanshan, Kuqa, and Khotan declined significantly, reflecting a shift in the architectural focus of Buddhism. This change was closely tied to the functional evolution of temple layouts: in earlier periods, stupas were the central structures of monasteries, carrying profound religious symbolism and significant functions. By the Tang Dynasty, however, Buddha halls, which were dedicated to enshrining Buddha images, gradually replaced stupas as the focal points of monasteries, shifting the focus of Buddhist activities toward these halls. This functional transformation diminished the importance of stupas within temple layouts, leading to their relative decline in numbers. Nevertheless, stupas continued to serve as symbolic representations of the Buddha, playing an important role in the Buddhist culture of the Western Regions.

The characteristics of different Buddhist sects also had a significant impact on the regional variations in stupa distribution. Theravāda Buddhism, which emphasizes personal practice, tended to favor the excavation of rock-cut caves as meditation sites. This sectarian feature resulted in a relatively lower number of stupas in the Kuqa region. In contrast, in areas such as Gaochang, where Mahayana Buddhism was predominant, stupas served as central structures for religious activities.

This section primarily explores the historical evolution of stupa distribution and its connection to political and cultural factors. During the Han Dynasty, stupas were primarily centered in regions like Shanshan and Khotan. In the Wei, Jin, and Northern and Southern Dynasties, their distribution expanded widely due to political influences. By the Tang Dynasty, Gaochang, dominated by Mahayana Buddhism, saw a relatively higher number of stupas.

4.2. The Evolution of Stupa Styles: From Simplicity to Diversification and Standardization

During the early stages of foreign cultural introduction, stupa design primarily reflected a direct adoption of external styles, with little to no localization. The design of Han Dynasty stupas closely resembled the original prototypes of Indian Buddhist architecture, featuring simple and singular base plan shapes, primarily circular or square. This direct continuation of design styles highlights Buddhism’s reliance on foreign architectural forms during its initial dissemination, while also indicating that local acceptance of Buddhist culture and architectural forms was still in the exploratory and adaptive phase.

During the Wei, Jin, and Northern and Southern Dynasties, the Western Regions gradually became a vital hub for cultural interaction and exchange. The power struggles among various ethnic groups introduced new cultural elements to the region, while the widespread dissemination of Buddhism further accelerated the fusion of foreign influences with local traditions. During this process, stupa architecture underwent continuous evolution, with base plan shapes transitioning from simple circular and square forms to more diverse designs. At the same time, the number of niches increased, and the design began to place greater emphasis on meeting the needs of religious rituals.

During the Tang Dynasty, stupa architecture matured while continuing the traditions established during the Wei, Jin, and Northern and Southern Dynasties. At this stage, the focus of stupa base design shifted from diversification to standardization, with architectural forms becoming more regulated and systematic. Stupa types largely adhered to the forms established in the previous period, concentrating on a limited number of major styles. Meanwhile, the number of niches further increased in the early Tang period but gradually declined later. The decorative style, influenced by Persian culture, began incorporating geometric patterns. This phase of stupa evolution signifies that Buddhism had entered a period of stability, with architectural forms increasingly tailored to meet the functional demands of the time.

This section primarily explores the gradual maturation of stupa styles as Buddhism spread and became localized. Initially, stupas directly borrowed from the prototypes of Indian Buddhist architecture, reflecting foreign cultural influences. Over time, during the Wei, Jin, and Northern and Southern Dynasties, stupa styles began to incorporate local elements, resulting in greater diversity to meet the religious rituals and cultural needs of different regions. By the Tang Dynasty, as Buddhism matured, stupa design entered a stage of standardization.

4.3. The Transformation of Stupa Symbolism: From Buddha’s Tomb to Mount Sumeru

In the context of early Buddhist culture, stupas served as tangible expressions of relic worship. During the 2nd century BCE to the 1st century CE, relic worship was particularly prominent in India [30]. Archaeological discoveries at the Sanchi stupa complex have revealed numerous relic containers housed within the kumbha-shaped structures of the stupa bodies. In the Niya Buddhist site and other locations such as L.B and L.E in Loulan, Andir No. 1 (Figure 10) and M.XI, M.XV, M.XII, M.XIII in Milan, the central spaces of the stupas are believed to have been used for displaying or venerating relics [31]. The discoveries of stupas used for interring relics at sites like the Sigqin Temple Grounds and Kizil Caves, as well as the findings of urns containing monks’ ashes within these stupas by Stein and Aurenberg, further support this [32]. Additionally, a wooden relic box unearthed by the 1903 Japanese Ōtani Expedition beneath a stupa at the Subashi site in Kucha also provides tangible evidence supporting our perspective [33]. As repositories of the relics (śarīra) of Śākyamuni, stupas served as the central objects of veneration for early Buddhist devotees, symbolizing the Buddha’s nirvāṇa.

During the Wei, Jin, and Northern and Southern Dynasties, the widespread proliferation of Buddha statues gradually diminished the stupa’s role as the sole focus of veneration. The worship of stupas transitioned into the worship of Buddha statues. As a symbol of Śākyamuni, the stupa had, in its earlier form, with the kumbha-shaped top, represented the Buddha’s nirvāṇa and sacred presence. However, the emergence of Buddha statues provided a more direct and tangible object of veneration for Buddhist devotees. Consequently, the symbolic role of Buddha statues partially replaced the central significance of stupas, leading to an increased focus on the former and a corresponding decline in the veneration of the latter.

In the evolution of Type Ca stupas, although the kumbha-shaped top remained an essential component, its visual prominence was gradually replaced by the Buddha statue, with its proportion and height significantly reduced, eventually evolving into the Type Da stupa. The square stupa base was often designed with niches to enshrine Buddha statues, further reinforcing the Buddha statue’s role as the focal point of veneration.

Type Cc stupas reflect a centralized compositional design, with their proportional arrangement emphasizing the prominence of the central niche. The vertical lines of the frontal staircase naturally guide the devotee’s gaze toward the niche, enhancing the visual focus. This design not only facilitates worship activities for devotees but also, through adjustments in proportion and composition, reduces the visual impression of upward extension, thereby further highlighting the religious significance of the stupa’s central structure.

Type Cc stupas, with their upper-level Buddha halls—although it is uncertain whether the original stupa retained a kumbha-shaped top due to structural collapse—represent the transition from stupas to Buddha halls. The presence of Buddha statues within these halls reflects a gradual shift in the function of stupas, from their original role as the tombs of the Buddha to spaces dedicated to the veneration of Buddha images. This transformation is not only evident in the architectural evolution but also signifies a shift in religious practice. Stupas, once primarily commemorative structures enshrining the Buddha’s relics, increasingly became integrated into the system of Buddha image worship, ultimately serving as an essential medium for the transmission of Buddhist beliefs.

Yijing once recorded: “The Sarvāstivāda school was divided into three branches… Only in Uḍḍiyāna, Kucha, and Khotan did practitioners of different branches coexist (有部所分, 三部之别……唯乌长那及龟兹, 于阗杂有行者)” [34], which suggests that at least three Buddhist sects coexisted in the Kucha region.

Studies on Buddhist caves in the Western Regions have revealed that different types of caves may be associated with different Buddhist sects [35]. Li Chongfeng, in Buddhist Archaeology: From India to China, argues that some of the central pillar caves in Kizil belong to the Dharmaguptaka school, while the Great Image Caves may also be related to this sect [36]. According to Zhao Ning’s research, the Kucha caves are primarily associated with the Sarvāstivāda and Dharmaguptaka schools, while also preserving traces of Mahāyāna and esoteric Buddhism [37].

The different sects of Theravāda Buddhism may also have been reflected in the design of stupas. Their understanding of cosmology and the differences in the scriptures they revered may have been concretely expressed through the structure, symbolic significance, and decorative elements of stupas.

The design of Type Cb stupas resembles the shape of a mountain, possibly reflecting the symbolic significance of Mount Sumeru or the Buddhist cosmological worldview. For instance, the Y site stupa at Gaochang displays distinct tiers, each gradually receding in size, as shown in Figure 11. This tiered structure closely corresponds to the description of Mount Sumeru in the Buddhāvataṃsaka-śāstra (佛说立世阿毗昙论):

“Mount Sumeru. From its summit downward, twenty thousand yojanas form the first tier, each extending fifty yojanas outward on all sides… From the summit downward, forty thousand yojanas form the second tier, broader than the first by fifty yojanas on each side… From the summit downward, sixty thousand yojanas form the third tier, extending outward fifty yojanas wider than the second… From the base of the ocean upward, fifty yojanas form the fourth tier, equal in breadth to the third, each tier extending outward by fifty yojanas (须弥山王. 从其顶上. 向下二万由旬. 是第一层. 是层四出. 并五十由旬. ……从顶向下. 四万由旬. 是第二层. 四出并广上层. 五十由旬. …… 从顶向下. 六万由旬. 是第三层. 四出并广二层. 五十由旬. ……从海水际. 向上五十由旬. 是须弥山王第四层. 广第三层. 五十由旬)” [38].

The Buddhāvataṃsaka-śāstra is an important Buddhist scripture related to Buddhist cosmology. It was composed no later than the 2nd century CE and is one of the canonical texts of the Sammitīya school, which originated as a branch of the Vātsīputrīya within Indian sectarian Buddhism [39,40]. This scripture was translated into Chinese by the Tripiṭaka master Paramārtha in 559 CE and has been included in various editions of the Buddhist canon throughout history. Although the Sammitīya school is classified as a branch of Theravāda Buddhism, it was widely practiced across Western India, Central India, Sri Lanka, and Southeast Asia between the 5th and 7th centuries CE. However, whether the Sammitīya school had any influence or presence in the Western Regions remains a subject that requires further scholarly investigation.

Figure 11. Representations of the Type Cb stupa: (a) Depiction of Mount Meru in Buddhist scriptures (Reprinted with permission from Ref. [41]. 2018, Wen Zhong); (b) Elevation view of Mount Meru from Buddhist scriptures (Reprinted with permission from Ref. [41]. 2018, Wen Zhong); (c) Example of a Type Be stupa (drawn by the authors).

Figure 11. Representations of the Type Cb stupa: (a) Depiction of Mount Meru in Buddhist scriptures (Reprinted with permission from Ref. [41]. 2018, Wen Zhong); (b) Elevation view of Mount Meru from Buddhist scriptures (Reprinted with permission from Ref. [41]. 2018, Wen Zhong); (c) Example of a Type Be stupa (drawn by the authors).

It is worth noting that the symbolic significance of this type of stupa form may not be limited to the stupa itself but may also be reflected in cave murals. For example, in the murals of the Tuyuq Caves, a tiered mountain structure (fortress pattern) appears (Figure 12), whose visual characteristics correspond to similar elements found in murals from Bamiyan and the Western Turkestan region [42]. Additionally, in this mural, the tiered mountain motif is positioned beneath a beaded motif featuring boar heads, suggesting a possible direct connection between the two.

Russian scholar Aurel Stein observed that in the nirvāṇa scene at the Kizil Caves, the pillow supporting the reclining Buddha was adorned with beaded motifs featuring boar heads, which may be related to the story of the Buddha’s nirvāṇa [10]. Miyaji Akira further pointed out that these motifs belong to the well-known Sasanian-style beaded boar motifs, which are not only found in the murals of Afrasiyab and Bamiyan but also appear on textiles unearthed from the Astana tombs in Turpan [43]. The widespread distribution of these patterns suggests that their symbolic meaning likely extends beyond simple landscape depictions and has become an important element within the Buddhist visual system, potentially carrying significant cultural connotations in Buddhist art.

Moreover, these patterns are found in the murals of Chamber A in Cave 38 of the Tuyuq Caves (Clements’ numbering), further reinforcing their possible religious symbolic significance. This cave consists of Chamber A with a transverse barrel vault and Chamber B with a longitudinal barrel vault opening at the front wall. Additionally, the passage between Chambers A and B was not excavated at the central axis of the wall, clearly indicating that the two chambers were not originally designed as an integrated cave structure. Grünwedel suggested that compared to Chamber B and its associated structures, Chamber A is of an earlier date [44]. According to Miyaji Akira, the central upper section of the front wall in Chamber B is adorned with a square, continuously arranged motif of the Seven Jeweled Trees in an Amitābha Pure Land scene. To the left (facing the front wall), a meditating monk is depicted, emanating flames and streams of water, while on the right, six strong young men are shown prostrating with both hands and feet on the ground above flames. The two sides may represent visualization scenes of the Pure Land by meditating monks, while the lower section features a scene of a demon attacking a Brahmin practitioner meditating under a tree, illustrating an impure visualization practice and a preaching scene [43]. Thus, this cave was highly likely designed as a Buddhist meditation cave, further confirming the overall Buddhist nature of Cave 38 and its connection to Buddhist cosmology. Coexisting within the same cultural and religious context, these chambers were likely intended to express related Buddhist themes.

Therefore, although it cannot be entirely ruled out that these mountain-shaped murals simply depict natural landscapes, their strong correlation with Buddhist cosmology, the imagery of Mount Sumeru, and the nirvāṇa narrative suggests that they are likely part of the Buddhist cosmological framework. This further supports the idea that the Type Cb stupa serves as a symbolic representation of Mount Sumeru, embodying the core essence of the Buddhist universe.

Additionally, as shown in Figure 13, the pedestal structure of the Type F Vajrasana stupas located in the central stupa forests of Jiaohe Ancient City and Gaochang Ancient City perfectly aligns with the description of Mount Sumeru in the Śarīraṅgīka-sūtra (《世记经》):

“其山直上. 无有阿曲……其山四面有四埵出. 高七百由旬……四埵斜低。曲临海上.”

“The mountain rises straight up, without any curves… On all four sides of the mountain, there are four projections (stūpas), each standing 700 yojanas high... These projections slope downward and lean toward the ocean” [45].

This five-stupa architectural layout may symbolize the esoteric Buddhist mandala system [46]. From the perspective of esoteric Buddhism, the mandala is not only a cosmic model but also a method of spiritual practice. The arrangement of the five stupas may correspond to the concept of the Five Tathāgatas in Vajrayāna Buddhism, with the central stupa representing Vairocana Buddha, while the four surrounding stupas symbolize the Four Directional Buddhas. Additionally, this structure may also represent the “Fivefold Dharmakāya” in Buddhism, symbolizing the five aspects of the Buddha’s Dharmakāya [47].

On the other hand, this architectural form may also be linked to the Buddhist culture of the Cheshi (Jushi) region [1]. As a significant Buddhist center along the Silk Road, Gaochang and its surrounding areas were influenced by multiple religious and cultural traditions. The evolution of stupa forms in this region likely reflects the unique development patterns of local Buddhist beliefs, shaped by the confluence of diverse cultural influences.

Figure 13. Representations of the Type F stupa: (a) Depiction of Mount Meru in Buddhist scriptures (Reprinted with permission from ref. [48]. 2017, Lixin Mao); (b) Elevation view of Mount Meru from Buddhist scriptures (Reprinted with permission from ref. [48]. 2017, Lixin Mao); (c) Example of a Type Be stupa (drawn by the authors).

Figure 13. Representations of the Type F stupa: (a) Depiction of Mount Meru in Buddhist scriptures (Reprinted with permission from ref. [48]. 2017, Lixin Mao); (b) Elevation view of Mount Meru from Buddhist scriptures (Reprinted with permission from ref. [48]. 2017, Lixin Mao); (c) Example of a Type Be stupa (drawn by the authors).

During the Han and Tang Dynasties, Mount Sumeru was typically depicted in a sandglass-shaped structure in cave murals (Figure 14). For example, in the murals of Dunhuang and Yungang, the visual representation of Mount Sumeru often takes the form of a sandglass, with its narrow waist coiled by dragons, symbolizing its sacred nature. In Xinjiang, such representations primarily appear in the Kizil Caves. Although similar depictions have also been found in the Tuyuq Caves, their appearance is relatively late, possibly resulting from the transmission of this stupa style from the Kucha region to Gaochang. From an archaeological perspective, no stupa sites with this structural form have been discovered in Xinjiang from the Han and Tang periods.

Buddhist scriptures also describe the sandglass-shaped form of Mount Sumeru. For example, the Abhidharma-kośa-bhāṣya (阿毗达磨俱舍论) states:

“Mount Sumeru consists of four tiers, each separated by 100,000 yojanas and extending outward by 160,000 yojanas, with widths of 8000, 4000, and 2000 yojanas, respectively […] the Thirty-Three Heavens are located at the summit of Mount Sumeru, with each side measuring 800,000 yojanas, identical in dimensions to the lower tiers […] at each of the four corners of the summit, there is a peak (须弥山共有四层, 每层间隔十万由旬, 并向外延伸十六万由旬, 宽度依次为八千, 四千, 二千由旬 […] 三十三天位于须弥山之巅, 其顶四面各宽八十万由旬, 与下层尺寸相同 […] 山顶四角各有一峰)” [49].

The mural themes in the Kizil Caves predominantly belong to the Theravāda Buddhist tradition, with most of their content traceable to the scriptures and Vinaya texts of the Sarvāstivāda school, while some themes appear exclusively in these texts [50]. The teachings of the Sarvāstivāda school were primarily based on the Abhidharma treatises [2]. This phenomenon suggests that Buddhist beliefs in Kucha and its surrounding regions were mainly influenced by the Sarvāstivāda school, and that this sect may have played a crucial role in the conceptualization of Mount Sumeru and its artistic representation.

During the Tang Dynasty, a large number of stupas featuring multiple niches began to appear, a phenomenon likely associated with the concept of multi-Buddha worship or the Thousand-Buddha belief in Buddhism. Thousand-Buddha worship originated from the “Great Thousand World” concept in Indian Buddhism and gradually emerged in the Northern Wei period, reaching its peak during the Tang Dynasty. Its development closely aligned with the emergence and evolution of multi-niche stupas.

Su Bai pointed out that the murals in the Kizil Caves exhibit characteristics of Mahāyāna Buddhism across different periods, which corresponds to historical records of Mahāyāna Buddhism’s spread in Kucha [51]. The rise of multi-niche stupas may have been driven by the popularity of the Thousand-Buddha belief, transforming stupas from mere commemorative structures symbolizing the Buddha’s nirvāṇa into concrete representations of the Thousand-Buddha worldview. The incorporation of multiple niches allowed devotees to worship from different directions, creating a spatial arrangement that mirrored the Thousand-Buddha depictions in cave murals. This architectural design not only reinforced the symbolic significance of stupas but also expanded their functional role in religious practice, establishing them as central structures in the Thousand-Buddha belief system.

Furthermore, the appearance of multi-niche stupas may also be closely related to the Mahāyāna Buddhist cosmological view. In Mahāyāna scriptures, the Buddha is not singular; instead, each world has its own Buddha, emphasizing the concept of “multiple Buddhas coexisting”. Consequently, during the Tang Dynasty, the number of niches in stupas increased to accommodate this religious principle. The spread of Mahāyāna Buddhism in Kucha further contributed to the transformation of stupas from being solely reliquary structures to becoming “Dharma Stupas” symbolizing the Buddha’s Dharmakāya. Within the Mahāyāna doctrinal framework, the Buddha’s Dharmakāya permeates the entire universe, transcending any singular form. Thus, the integration of the Thousand-Buddha belief with stupas represents a material expression of this concept.

This section explores the transformation of stupa symbolism, from serving as a representation of the Buddha’s relics in early Buddhism to embodying the cosmological concept of Mount Sumeru. During the Han Dynasty, stupas were characterized by prominent kumbha-shaped tops, emphasizing relic worship. In the Wei, Jin, and Northern and Southern Dynasties, the rise of Buddha statue worship gradually replaced the stupa’s central religious role, while stupas began to evolve into symbols of Mount Sumeru. By the late Tang Dynasty, with shifts in religious beliefs and the further clarification of temple architectural functions, the symbolic significance of stupas as representations of the Buddha further diminished.

4.4. The Evolution of Stupa Niches: Few to Many to Few

The evolution of niche types reflects the transformation of stupa functions and religious rituals. During the Han Dynasty, stupas were mostly constructed without niches, a design that reflects the worship practices of early Buddhism. In Buddhist belief, after the Buddha’s parinirvana, his physical form became invisible. However, his presence could be symbolized through objects associated with him. As a result, early Buddhism lacked Buddha statues, and symbols such as stupas and bodhi trees were used to represent the Buddha. In Han Dynasty stupas, high bases were commonly built to elevate the stupa dome, emphasizing the stupa’s prominence and reflecting the reverence for stupas as key symbols of Buddhist devotion.

Over time, the object of Buddhist worship gradually transitioned from stupas to Buddha images. During the Wei, Jin, and Northern and Southern Dynasties, all stupas constructed during this period incorporated niches, signifying this pivotal shift. With the rise of Three-Buddha worship, a few niches began to appear to house statues of the Three Buddhas. For example, in the central stupa at site E-28 of the Jiaohe Ancient City, a small adobe platform was carved into the rear and east and west walls of the stupa chamber, likely for enshrining three statues, possibly representing the Three Buddhas [27]. This transformation had a profound impact on the stupa’s role, leading to a gradual decline in its symbolic prominence, with the proportion of the hemispherical dome also becoming noticeably smaller. Simultaneously, Buddha images began to be integrated into the stupa base, which saw an increase in height and proportional emphasis. Niches were deliberately added to the stupa base to enshrine these images, reflecting the growing importance of Buddha statues in religious practices and the evolving architectural response to changing devotional needs during this period.

In the Tang Dynasty, a large number of stupas with multiple niches began to appear, a phenomenon likely related to the concept of multi-Buddha worship or Thousand-Buddha worship in Buddhism.

At the same time, some stupas originally featuring multiple niches gradually evolved into forms with few or no niches. This shift may be related to the increasing specialization in the functional division of Buddhist temples. With the widespread practice of Buddha image worship, Buddha halls gradually became the core architectural feature of temples, dedicated specifically to housing Buddha statues, thereby replacing stupas in their role of enshrinement. As a result, stupas came to serve more as symbolic and commemorative structures, with their façades no longer requiring multiple niches for Buddha statues.

This evolution reflects the dynamic progression of Buddhist beliefs across different historical stages. In the early phase of Theravāda Buddhism, stupas typically lacked niches, symbolizing the enshrinement of the Buddha’s relics. During the Wei, Jin, and Northern and Southern Dynasties, stupas began incorporating niches to accommodate religious practices, with Three-Buddha worship being prevalent. During the Mahāyāna period, the flourishing of Thousand-Buddha worship led to the incorporation of multiple niches into stupa designs, accommodating this extensive devotional practice. However, with the further functional specialization of Buddhist temples and the emergence of Buddha halls as the core structures, stupas gradually transformed into symbolic commemorative monuments. Their niches reverted to fewer or none, possibly reflecting a return to Theravāda traditions in later periods.

4.5. The Symbolic Significance of the Stairway

The stupa’s base often features steps leading up to the foundation of the stupa. For example, the Great Buddha Temple in Yingpan Monastery and Pagoda No. 2 at Mo’er Temple both have centrally positioned steps on one of their sides. These steps can be seen as an extension of the central pillar. In many ancient cultures, a celestial ladder was regarded as a bridge connecting the earth and the heavens, serving as a pathway to the realm of the divine. This concept is also present in Buddhism. As Dīrgha Āgama Sutra (长阿含经) states, “the King of Mount Sumeru has a pathway of seven precious steps, with the lower steps measuring sixty yojanas in width (须弥山王有七宝阶道, 其下阶道广六十由旬)” [45].

These seven treasures’ steps symbolize the path to ascension, and the gods of the heavens are said to descend to earth through this passage [52]. By ascending these steps, devotees symbolically reach the base of the stupa, which is connected to the cosmic center, enabling communication and interaction between humans and the divine.

The stupa’s stairway symbolizes a celestial bridge connecting the earthly and divine realms, reflecting Buddhist cosmology and serving as a pathway for devotees to engage with the cosmic center.

4.6. Limitations and Future Work

Due to the limitations of archaeological data, the lack of sufficient information from certain regions presents challenges to forming comprehensive conclusions about the regional distribution of stupas. The incomplete excavation of some sites leaves the architectural characteristics and spatial distribution of stupas in these areas underrepresented. These gaps in sample coverage not only hinder the accurate classification of stupa distributions but also reduce the clarity and reliability of regional comparative analyses.

The preservation status of archaeological sites plays a critical role in typological research. Many sites, affected by natural erosion, historical damage, or long-term neglect, may no longer preserve key architectural features in sufficient detail. This issue is particularly pronounced when studying the finer characteristics of certain types. For instance, the precise proportions of hemispherical domes or the specific details of base decorations may be difficult to determine due to site deterioration. Consequently, this lack of clarity can hinder accurate classification and limit the analysis of the evolutionary patterns of these stupa types.

This study does not comprehensively cover the historically broader concept of the “Western Regions” but instead limits its scope to the modern Chinese Western Regions. Given the complexity and frequent shifts in the political landscape of the Western Regions during the Han and Tang Dynasties, this study adopts a modern framework to simplify the division of regions and periods. However, this approach may not fully capture the dynamic changes in the historical context. Additionally, the lack of sufficient data to determine the exact construction time and regional affiliation of certain stupas may somewhat affect the comprehensiveness and accuracy of the research findings.

Future research can focus on conducting comparative studies across multiple regions, utilizing digital modeling and interdisciplinary approaches to explore the cross-cultural transmission and diverse expressions of Buddhist architectural styles. By integrating archaeological findings, historical documents, and advanced technologies, such as 3D reconstructions, future studies can provide deeper insights into the dynamic evolution of Buddhist architecture and its adaptation to various cultural and environmental contexts.

By expanding the depth and scope of research, future studies will provide more comprehensive insights into the regional characteristics and evolutionary patterns of Buddhist stupas in the Western Regions during the Han and Tang Dynasties, making greater academic contributions to architectural history, archaeology, and cultural transmission studies.

4.7. Discussion Summary

The discussion explores the historical evolution of stupa architecture in the Western Regions, focusing on distribution patterns, stylistic development, symbolic transformations, and niche evolution. Key findings reveal that stupa designs progressed from simple, relic-centered structures during the Han Dynasty to diverse and localized forms in the Wei, Jin, and Northern and Southern Dynasties, and ultimately achieved standardization in the Tang Dynasty. Symbolically, stupas transitioned from representing the Buddha’s relics to embodying the cosmological concept of Mount Sumeru, reflecting shifts in religious practices and temple architecture. These findings highlight the dynamic interplay between Buddhist beliefs, cultural adaptation, and architectural styles.

5. Conclusions

This study adopts typological analysis as its core methodology to systematically explore the architectural evolution and cultural connotations of Buddhist stupas in the Western Regions during the Han and Tang Dynasties. By integrating historical geographical distribution and proportional changes, the study reveals the spatial and temporal patterns of stupa dissemination during this period. The key findings are as follows:

1. During the Han Dynasty, Buddhist stupas were concentrated in transportation hubs such as Shanshan, Khotan, and Kashgar. In the Wei, Jin, and Northern and Southern Dynasties, the distribution range expanded due to the spread of Buddhism and political demands, with the dissemination focus gradually shifting from Shanshan and Khotan to Gaochang and Kuqa. In the Tang Dynasty, the number of stupas in Gaochang became particularly prominent; however, the overall number of stupas slightly declined. This change was closely related to the shift in the spatial focus of temple layouts, which increasingly centered around Buddha halls, as well as the prevalence of Theravāda Buddhism in regions such as Kuqa.

2. The styles of Buddhist stupas exhibit an evolutionary pattern of transformation from simplicity to diversification and eventual standardization across different periods. During the Han Dynasty, stupas were characterized by a hemispherical dome design with a simple and minimalist style. Their base plan shapes were primarily circular or square, emphasizing their commemorative function as reliquary structures. In the Wei, Jin, and Northern and Southern Dynasties, stupa designs became increasingly diverse, incorporating multi-tiered structures and niches, which marked a gradual localization of stupa styles. By the Tang Dynasty, stupa designs, while continuing earlier traditions, achieved greater standardization through precise proportions and geometric symmetry, further enhancing the cosmic symbolism of Mount Sumeru in their architectural expression.

3. The evolution of niches in Buddhist stupas demonstrates a transition from fewer to more and then back to fewer over time. During the Han Dynasty, stupas were primarily designed without niches, emphasizing their commemorative function and using elevated bases to highlight their symbolic status as the center of religious devotion. In the Wei, Jin, and Northern and Southern Dynasties, the number of niches increased significantly, marking a shift in Buddhist practices from stupa worship to Buddha image worship. Niches were incorporated into the stupa base to accommodate the growing need for Buddha image veneration, leading to adjustments in architectural proportions and the elevation of stupa bases. In the early Tang Dynasty, the use of multiple niches aligned with the concept of the “Thousand Buddhas”, reinforcing the religious symbolism of stupas. However, as Buddha image worship gradually shifted to Buddha halls, the role of stupas became more commemorative, and the number of niches began to decrease. This evolution reflects the transformation of Buddhist beliefs and the functional differentiation within temple architecture.

4. The changes in the proportions of Buddhist stupas reflect shifts in their cultural and symbolic significance. During the Han Dynasty, stupas emphasized the proportion of the hemispherical dome, symbolizing the core functions of Buddha’s nirvāṇa and relic worship. In the Wei, Jin, and Northern and Southern Dynasties, the proportion of the hemispherical dome gradually diminished, while the base proportion increased, symbolizing Mount Sumeru as the cosmic center. By the Tang Dynasty, stupas achieved a harmonious integration of religious cosmology and architectural form through standardized proportional designs and tiered, tapering base structures, completing a transformation from commemorative to symbolic functions.

This study reveals the process of dissemination and cultural adaptation of Buddhist stupas in the Western Regions during the Han and Tang Dynasties, enriching the understanding of the diversity in stupa architectural forms and their cultural significance. However, the study is limited by its focus on the Western Regions. Future research could expand to comparative studies across multiple regions, incorporating digital modeling and interdisciplinary approaches to further explore the cross-cultural transmission and diverse expressions of Buddhist architectural styles.