**1. Introduction**

The concept of historic districts first appeared in The Athens Charter. Buildings and districts of historical value shall be appropriately preserved and shall not be destroyed [1], distilling buildings and districts of historical value into a single category. The concept of historic districts was introduced in The Washington Charter, which defined them as cities, towns, historical centers, and residential areas, regardless of their size, and also their natural and manufactured environments [2]. The introduction of this concept extended the original concept of buildings and districts of historical value to include the environments in which they are located. Historic districts refer to areas where the architectural heritage is more concentrated or where the traditional style and local characteristics of a certain period are better reflected intact. However, with the accelerating urbanization, many cities with traditional historic districts are undergoing large-scale urban renewal. Although the physical environment of historic districts has been improved, the spatial form of historic districts has been severely damaged by massive demolition and construction [3]. Historic districts are still trapped in a situation of insufficient spatial group vitality, lack of spatial quality, and lack of regional culture. Many of them lack daily activities for residents to maintain vitality and meet the growing social needs [4]. Historic districts are facing the problem of balancing development and conservation [5]. In order to retain urban diversity and vitality, historic districts with diverse roles and appropriate scales must be preserved [6,7] but also for preserving traditional urban culture.

China State Council published the initial administrative document on urban planning in February 2016. The document highlights the need for orderly urban restoration and organic renewal, addressing issues with environmental quality degradation, spatial disorder, and the destruction of historical and cultural heritage in old cities, restoring the functions and vitality of old cities, better preserving the historical heritage, and presenting the urban landscape [8]. The historic quarter is, without a doubt, the source of the city's life. The historic district keeps the artifacts' vibrant real-life history and true historical knowledge intact. It has a certain size that may accurately capture the special qualities of

**Citation:** Liang, W.; Ahmad, Y.; Mohidin, H.H.B. Spatial Form and Conservation Strategy of Sishengci Historic District in Chengdu, China. *Heritage* **2023**, *6*, 891–903. https:// doi.org/10.3390/heritage6020049

Academic Editors: Lucia Della Spina, Paola Pellegrini, Antonia Russo, Maria Rosa Valluzzi, Angela Viglianisi, Giovanni Castellazzi and Rafael Fort González

Received: 15 November 2022 Revised: 30 December 2022 Accepted: 12 January 2023 Published: 20 January 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

a particular historical era, a particular nationality, or a particular location. It serves as a vehicle for preserving the city's historical culture and displaying the urban environment. In the environment of urban renewal, it is inevitable to explore and analyze its spatial form to find a targeted conservation strategy. The urban form depends on the interaction between people and urban public space, and the intertwined processes of people's activities and places of residence make urban life more diverse and dynamic [6,9]. The Venice Charter promotes the original conservation of the historic spatial environment [10]. Urban space can be defined as a perception revealed by the urban fabric [11–13], a social and cultural phenomenon that shapes the relationship between people and the environment [14]. This scene forms a way of daily life, capable of meeting people's needs [15]. In particular, street networks are a long-term component of the urban form [16–19] and are an essential driver in the urbanization process [20], with street layout identified as a significant factor influencing pedestrian movement in cities [21–24]. Data-based urban morphology attempts to model spatial data to track urban morphology, spatial order, configuration, and orientation, and one approach is the space syntax.

Understanding urban space in its physical, morphological, and social components is made possible by the space syntax [25–27], providing a different approach that focuses on topological aspects of urban morphology to estimate the supportiveness of the built environment. The space syntax initially focused on city pedestrian movement [22,28]; however, further research discovered a strong correlation between topological measures and social engagement [29–31]. This circumstance can clarify the connection between spatial shape and human behavior in the environment [27]. The Sishengci historic district has a long history, and it is crucial to study the spatial form of the historic district to conserve the spatial form of architectural heritage. In order to solve the problem of social integration of the residents in the historic district and to maintain the sustainable organic vitality of the district, this study is a methodological exploration of conservation and renewal in the Sishengci historic district, uses the space syntax of the axial lines analysis method, discusses the analysis of the historic district and its development law from a rational point of view, quantifies the interpretation of the spatial form of the historic district, and proposes the strategy of conservation and renewal of the historic district here to meet the social integration of the residents.

#### **2. Methodology**
