**6. Case Studies**

### *6.1. Ajanta Caves and Underground Temples, India*

For this article, we analyzed the Buddhist compound of Ajanta in the Wagora River, India, in detail. This consists of more than 30 artificial caves with either statues of the Buddha or frescoes of its past miraculous lives, also known as jataka [11,12]. The caves were excavated around the 5th century A.D. and could be clear precedents of the Silla Buddhist' temples of Korea (analyzed in Case Study 2).

In these famous underground temples, named Chaitya, daylight comes exclusively from an unglazed aperture, which resembles the semicircular mouth of a tunnel, although more prone to architectural expression. The reason behind these highly inspiring constructions is altogether sustainable (Figures 12 and 13).

When the Buddhist monks could not wander in pilgrimage preaching the doctrine of the dharma due to harsh monsoon weather, they instead decided to honor Shakyamuni by building stupas inside the cliff. In this manner, they protected themselves from discomfort, but still kept expounding the sutra, by virtue of prodigious images, to future believers.

The tunnel-like constructions were necessary to have some light and air during this hard but refined work, whilst the thermal inertia of the rock moderated the excessive oscillations in such a torrid region. Any waste material was accommodated in a natural fashion to the surroundings.

**Figure 12.** Section of Chaitya number 19.

Let us for instance describe the analysis performed in cave number 26 (Figure 14), which shows a western orientation that is ideal for ceremonies in early morning or evenings, depending on the season of the year.

**Figure 13.** (**a**) View of the entrance to Chaitya number 26. (**b**) Interior stupa showing the sculpture of the Buddha.

By late summer, after the inevitable rainy season, the sky is cloudy (technically, overcast) and the illuminance levels may reach 10,000 lux. Assuming the radius of the opening to be 2 m and the span to the inner shrine is 14 m; we employed our tunnel shape simulation model to obtain, on the horizontal plane, values of only 6 lux. This means a very scant level of light (Figure 15).

**Figure 14.** Graph of illuminance distribution in the chaitya. Source: Cabeza-Lainez.

Forewarned by this result, we suggested to the restoration team that inner reflections would be critical to perform any activities in the space, and that the materials employed should have enhanced extreme diffusion of light. Not much later, archaeological evidence corroborated this fact in remnants of stucco, gilt, or inlayed areas, and other kinds of reflective veneers.

**Figure 15.** Plans of Chaitya 26 of Ajanta (India) with day-lighting values (3000–50 lux). Source: Cabeza-Lainez.

This was one of the first experiences with hypogeal precincts in Asia in which first-hand knowledge of sustainability through lighting was attained, but also in that it could help to raise meaningful restoration efforts.

### *6.2. The Seokguram Grotto, Gyeongju, Korea*

Stimulated by our initial experience outside Europe, the Kyungil University invited us to research at another temple excavated in the mountain, which is in fact of paramount heritage for the Republic of Korea. It is also controversial from the point of view of political sustainability since it had been unearthed at the time of Japanese domain, and maintained for years in neglect and disrepair.

We had to carefully study the geometry and characteristics of the Seokguram Grotto (Figures 16–18), not only in connection with the sunlight, but also to determine the structural stability of the cupola enshrining the magnificent Buddha statue [13].

**Figure 16.** Geometric exactitude and proportions of the Seokguram artificial cave.

**Figure 17.** An interior view of the Buddha sculpture on a lotus pedestal. Source: Juhyung Lee.

**Figure 18.** Model of Seokguram underground temple. (**a**) View from the entrance of the model. (**b**) Interior with proportions and dome. Source: Salguero-Andujar.

We simulated the resistance and solidity of the new structure (Figure 19), which incorporated only fragments of the ancient one. The type of stone and the soil mechanics around the tumulus were also calculated [13].

**Figure 19.** An example of the simulation model employed to find the stresses of the special type of granite stone employed for the dome. Source: Salguero-Andujar.

Finally, regarding the lighting conditions, we were asked to simulate the possibility of a circular opening with a diameter of 0.8 m in the low eastern area of the dome (Figure 20), which has been lost, according to evidence and other sources. Since this chamber is a spherical cap, the use of the equations presented in the previous chapters of the article was almost immediate and the results encouraging. However, we have to say that such a window would permit adumbrating the Statue of the Buddha, but common activities inside the temple would have to rely on reflections as in the case of Ajanta, or some sort of artificial lighting (Figure 21). We hope that in the near future and following our stint, some perforations of the dome could be implemented in accordance with a much more e fficient electrical system.

**Figure 20.** Radiative model of Seokguram underground temple. (**a**) Tentative location of the archaeological opening (**b**) Distribution of daylight in the plan of the shrine, generated by the simulation software. Average values of 17.95 lux. Source: Cabeza-Lainez.

**Figure 21.** Sectional view of the grotto including lighting levels by a surmised circular opening. Source: Rodriguez-Cunill.

### *6.3. The Nantang Cathedral in Beijing, China*

The third example discussed in this paper is no longer an extant catholic church in Beijing. It was built by Jesuit Missionaries at the beginning of the 17th century, but suffered several disasters until it was ruined by the second Opium War in the 19th century.

A new church was erected on the site, but it does not retain any of the excellent features that the former incorporated. The ancient church was a paradigm of Sinicization, as we will try to demonstrate (Figure 22).

The Jesuits had prepared detailed plans and a very unusual drawing perspective to facilitate the construction of the church.

Many curious features appear in the original drawings that the Portuguese Historic Archives maintain today. One of them is the triple ceremonial gate flanked by stone lions to protect the building from evil spirits.

**Figure 22.** South façade of the Nantang Cathedral, reconstructed from the original plans preserved at the Arquivo Historico Ultramarino (Lisbon. Source: H. Ojeda and J. Cabeza-Lainez).

The plans present writings in Portuguese language, but detailed inscriptions in Chinese also appear. One such inscription shows the cardinal points or directions of Heaven, as mentioned in Daoist scriptures, specifically indicating that the main façade has to face due south for the same reason of harmonizing with the cosmos and to avert calamities [14].

Based on such magnificent drawings the authors have accurately reconstructed the floor plan and façade with the help of CAD systems.

The elevations reveal that the fundamental source of lighting was the main façade oriented to the south, which was in striking contrast with Catholic churches in Europe that usually face west, according to the authors' own surveys and measurements [8,15]. Here instead, slender framed windows are the sole elements of fenestration.

The overall style of the building did not resort to classic ornaments to resolve typical problems of expression, but rather seems to adopt baroque features as a starting point to create something new and capable of accommodating Chinese sensibility.

The Jesuits at the Qing Court had justly excelled in astronomical knowledge and subsequent control of time by manufacturing watches, astrolabes, and other mechanical tools of measurement for the Emperor. This fact is elegantly marked in the cathedral with the inclusion of two voluminous clocks at each side of the main façade, simultaneously displaying the time in Beijing and that of Rome.

The former indicates that they had guessed by exchanging letters in the occasion of eclipses, about the significant magnitude of the time lag between both places, although they were still unable to trace a meridian [15].

In this case, the simulation included the curved elements of the vaults that the European missionaries introduced as a novelty for interior spaces. The vault and the dome had not developed much in Eastern Asia for several reasons including the want of compressive materials and weather tending to heavy rains and winds [14].

In Figure 23, we present the trajectories of solar movement for the vicinity of the church and its probable exposure to sunlight.

**Figure 23.** Daylighting model of Nantang Cathedral. (**a**) Solar Chart for Beijing. (**b**) Solar exposure at different hours. Source: Cabeza-Lainez.

Figures 24 and 25 depict a more vectorial approach to the radiation phenomena of the interior for the situations of summer and winter.

As previously stated, the key here is the southern orientation of the main façade, which is very unusual in the West, but required from cosmological and cultural points of view. Such disposition may have contradicted the catholic liturgy on many occasions.

**Figure 24.** Radiative field inside the church in winter. Source Cabeza-Lainez.

The levels were revealed to be adequate for the performance of activities in the range of 400 lux. This is important because most Chinese temples and precincts were dark and gloomy and a new religion could easily prove its supremacy by revealing even the darkest corners of its faith by means of its architecture.

If harmony with thesun and environment is demonstrated by virtue of architecture, it is easier to spread any belief that is taught precisely at that architecture. The Jesuits were always conscious of such a fact in all of their churches [16].

**Figure 25.** Summer distribution of radiation for the Nantang Cathedral. Source: Cabeza-Lainez.

Except for the façade, the exterior of the church remains simple in character. However, from another original etching, we know that the interior was lavishly decorated, the ceilings were vaulted with carved and painted wooden panels using naturalistic motifs. It is on the inner walls of the Cathedral that the spectacular frescoes of Giuseppe Castiglione once stood.

Master Castiglione, or Lang Shining in Chinese, was considered by many to be the last grea<sup>t</sup> Chinese painter who used another European effect to beckon the believers: focal perspective. As a curiosity, we reconstructed the following descriptions of the contemporaries of some of the paintings that once adorned the interiors conceived by Castiglione. We can only regre<sup>t</sup> that they are lost ... forever? (Figure 26).

**Figure 26.** Frescoes by Giuseppe Castiglione. (**a**) Reconstruction of Nantang Cathedral. (**b**) Inside the JuanqinZhai (Pavillion at the Forbidden City) pergola of wisteria. Source: Rodriguez-Cunill.
