Architecture of Kinh Thien Palace in the Early Le Dynasty

Researching and decoding the architectural morphology of ancient palaces in Thang Long Imperial Citadel in general and Kinh Thien Palace in particular is an extremely difficult problem - This is truly a big challenge for scientists , due to the lack of sources of documents.

Over the past years, based on archaeological and historical sources and comparative research results with ancient palace architecture in East Asia, the research team of the Imperial Citadel Research Institute, led by Associate Professor, Dr. Bui Minh Tri, has successfully deciphered and reconstructed the architectural form of palaces during the Ly and Tran dynasties (2016-2020) and recently Kinh Thien Palace (2020-2021). Although these are only initial research results, they have provided quite convincing images - Because they are based on many reliable and authentic scientific bases, helping us to visualize more clearly the unique beauty of the ancient Thang Long Imperial Palace architecture with the similarities and differences of Vietnamese palace architecture in the history of ancient palace architecture in East Asia.

Image of Long Thien Palace built during the Nguyen Dynasty on the foundation of Kinh Thien Palace during the Early Le Dynasty, taken by the French in 1886 (Source: EFEO)

Stone steps of Kinh Thien Palace, early Le Dynasty, in the present-day Hanoi Citadel. Source: Bui Minh Tri

Part 1: Wooden structure and shape of the telescopic roof support frame

Introduction : Kinh Thien Palace is the court palace located in the center of the Forbidden City of Thang Long Capital during the early Le Dynasty. This palace was built by King Le Thai To in 1428 after defeating the Ming army (1407-1427), ascending the throne and rebuilding Thang Long Capital. According to official history, the palace was repaired and rebuilt in 1465 and 1467 and was used for a very long time through 3 dynasties: the early Le Dynasty (1428-1527), the Mac Dynasty (1527-1593) and the Later Le Dynasty (1593-1789) (Complete Annals of Dai Viet, 2011). After more than 388 years of existence, Kinh Thien Palace was completely destroyed in 1816 when the Nguyen Dynasty (1802-1945) built a new Hanh Cung Palace in the area of this main palace (see Figure 1). The only vestige of the golden memories of Kinh Thien Palace remaining is the stone steps carved with dragons in the center of the Thang Long Imperial Citadel Heritage Site (Hanoi) today (see Figure 2). All the architectural works of the palace, pavilions, pagodas, and communal houses in the ancient Thang Long Imperial Citadel have been buried underground. Because they were destroyed long ago and there are no historical documents, images, or drawings describing the architecture of the main hall, today we cannot know the appearance, scale, and architectural form of Kinh Thien Palace. And accordingly, the research to restore Kinh Thien Palace, which plays an extremely important role in the history of Thang Long Capital, has become extremely difficult due to the lack of sources of documents.

Architectural vestiges of the early Le dynasty pillar foundation on the east side of Kinh Thien Palace (Source: Bui Minh Tri)

Stone base for columns from the Early Le Dynasty found at Thang Long Imperial Citadel (Source: Bui Minh Tri - Nguyen Quang Ngoc).

In order to have a scientific basis for the overall study of the Kinh Thien Palace space, especially the study of the restoration of the Kinh Thien Palace, from 2011 to present, dozens of archaeological excavations have taken place around the Kinh Thien Palace area. The results of excavations and archaeological research over the past 10 years have brought to light many valuable new discoveries, providing more reliable scientific evidence for the study of decoding the Kinh Thien Palace space and the architectural form of the palace during the early Le Dynasty, especially the main hall in the Thang Long Forbidden City (Tong Trung Tin, 2022). Historical books and written documents recording the construction of the palace architecture of the Thang Long Imperial Palace during the early Le Dynasty seem to be extremely rare and unclear. Therefore, the above archaeological sources are considered the most important and the most reliable scientific basis for the study of decoding the architecture of Vietnamese palaces during the early Le Dynasty. In the light of these sources, the palace architecture in Thang Long Imperial Citadel is gradually being revived with science, through academic research aimed at decoding the mysteries of architectural forms.

Citadel architecture in Northern Vietnam – 1: Bui Ke Pagoda (Hanoi); 2: Keo Pagoda ( Thai Binh ); 3: Tay Dang Communal House (Hanoi)(Source: Institute for Monument Conservation, 2017 (1,2); Institute for Imperial Citadel Studies(3).

Research on decoding architectural morphology – That is, research on decoding architectural style. And the fundamental approach to the case of Kinh Thien Palace is to analyze archaeological sources excavated at the site, combined with historical documents and comparative research results with existing traditional architecture and ancient palace architecture in East Asia. In this research method, the most important thing is to research and analyze the foundation plan, the roof support frame and the roof of the building. In other words, it is necessary to research and decode the architectural type and structure of the architectural frame, based on the study of the foundation structure (or architectural plan) and the types of materials, types of wooden components related to the architecture, on that basis, we can have an understanding of the characteristics or architectural style. Based on the drawings, models and research results analyzing the types and functions of wooden structures and roof tiles excavated at the site, combined with comparative research with the traditional architecture still existing in Northern Vietnam today and ancient palace architecture in East Asia, especially the palace architecture of the early Ming Dynasty through the Doanh Tao Phap Thuc documents and through field research at ancient palace relics in the Forbidden City of Beijing (China) or Changdeokung (Korea) and Nara (Heijo - Japan), ... this article will initially publish the research results of decoding and reconstructing the architectural form of the palace of the early Le Dynasty through the case of Kinh Thien Palace. This is also the basis for the orientation of international academic research on the history of Vietnamese palace architecture in the context of the history of ancient palace architecture in East Asia.

Image of a two-story citadel architecture painted on Vietnamese exported ceramics, early Le Dynasty, 15th century (Source: Bui Minh Tri)

1. Wooden structures and analysis of the roof support frame system Thang Long Imperial Citadel is a famous archaeological site of Vietnam, located in the center of Hanoi Capital. This site was excavated on a large scale in 2002-2004, 2008-2009, 2012-2014 including the following locations: 18 Hoang Dieu, National Assembly Building Construction Area, 62-64 Tran Phu. The excavation results found many traces of the foundations of wooden architectural works and many types of relics from many periods, overlapping and intertwined in a very complex manner, from the Dai La period, Dinh - Tien Le period to the Ly, Tran, Le So, Mac and Le Trung Hung periods (from the 7th-9th century to the 17th-18th century). These are very important discoveries, vividly demonstrating the continuous and long-lasting existence of Thang Long Citadel over more than a thousand years of history (Bui Minh Tri - Tong Trung Tin, 2010; Bui Minh Tri, 2016). From the important archaeological discovery, in 2010, the relic site was recognized by UNESCO as a World Cultural Heritage.

Various types of vases and wooden heads from the Early Le Dynasty found at the Thang Long Imperial Citadel relic site (Source: Bui Minh Tri - Nguyen Quang Ngoc)

Underground archaeological discoveries have confirmed that the palace architecture in the ancient Thang Long Imperial Palace was all wooden architecture, with a wooden load-bearing frame, and the roofs of the structures were covered with very typical types of tiles (Bui Minh Tri - Tong Trung Tin, 2010; Bui Minh Tri, 2016). At the 18 Hoang Dieu relic and the Kinh Thien palace area, in addition to the traces of the Le So dynasty architectural foundations that were firmly reinforced with broken bricks and tiles, excavations have found quite a few stone bases supporting the wooden columns of the structure (see Figure 3-4). Although these stone bases have many different sizes, they are all made of opaque white limestone and have a fairly uniform shape. They are the type of base without decorative patterns, with a square base, a round trapezoidal body, and are about 5-8cm higher than the average square surface, with a flat surface. Based on this feature, it can be known that this is the type of base supporting round wooden columns. In other words, the wooden pillars of the palace architecture in the early Le Dynasty were commonly round pillars. The pedestals here come in many different sizes, the small ones have a face diameter of 38-48cm, the large ones have a face diameter of 50-60cm, and there are also larger ones with a face diameter of over 70cm, but they are very rare. Based on these sizes, it can be inferred that the small pedestals used to support the pillars in the porch and porch columns have an average diameter of about 36-46cm; the large ones used to support wooden pillars inside the house, also known as main pillars, and these pillars have an average diameter of about 48-58cm.

Research on the reconstruction of the fortification structure of the Early Le Dynasty based on the wooden structure documents excavated at the Thang Long Imperial Citadel relic site (Source: Bui Minh Tri - Nguyen Quang Ngoc)

In the excavation pit east of Kinh Thien Palace in 2018, a red-lacquered wooden column 228cm high, with a base diameter of 38cm, was excavated, corresponding to the type of stone base supporting the column in the above-mentioned porch. Notably, in the excavation pits in this area, many types of wooden components of the roof support frame of the structure were also found. Research on wooden components and comparison of analyzed wood samples showed that the architectural works of the Early Le Dynasty were mainly built with precious woods in the four-wood group (dinh, lim, sen, tau), of which many were sen mat, tau mat and lim (Bui Minh Tri, Nguyen Thi Anh Dao 2015:136-137). Because the palace architecture of the early Le Dynasty was completely destroyed, the discovery of traces of foundations, types of wooden structures or types of roof tiles is identified as important and very meaningful documents in the study of contemporary architecture. However, in order to gain an understanding of the architectural form, the most important thing is to study and decode the roof support frame, or in other words, to study and decode the architectural type and structure of the architectural frame. In the journey of collecting documents and conducting comparative research, an important issue was raised: what architectural style was the frame structure of the palace architecture of the early Le Dynasty built in: (1) In the style of "stacked beams" or "transmitted beams", similar to the traditional religious architecture in Northern Vietnam today? (2) In the style of "dau cong", similar to the architecture of the Ly and Tran dynasties? These are the big questions raised when orienting research to decode the roof support frame system and architectural morphology of Vietnamese palaces.

Comparative study of the structure of Vietnamese dou gongs in the early Le Dynasty with Chinese dou gongs in the early Ming Dynasty (Source: Ngo Vi - Bui Minh Tri - Nguyen Quang Ngoc)

In a number of previous research works, based on archaeological data, model data and epigraphic data, we have demonstrated that the palace architecture in the Thang Long Imperial Palace during the Ly - Tran dynasties was mainly dou cong architecture. This is considered a very important observation, the key in the study of decoding the architectural form of the palace in the Thang Long Imperial Palace. The results of this research were also published at international scientific conferences in China and Korea in 2018 (Bui Minh Tri, 2016; 2018; 2019). For the history of ancient East Asian palace architecture, dou cong architecture is a common term and a symbolic image of the culture and art of royal architecture of the monarchical dynasties. In China, Japan or Korea, the palace architecture of the dynasties that still exist today are all dou cong architecture, with tiled roofs. This type of architecture is considered a Chinese invention, with a long history dating back to the Spring and Autumn period more than 2,500 years ago and its influence has spread to countries of the same culture in East Asia. For the history of Vietnamese architecture, dou gong or dou gong architecture seems to be an uncommon concept, even a very strange issue for many researchers. Because the Vietnamese palace architecture from the Dinh - Ly - Tran - Hau Le dynasties (from the 10th century to the 18th century) no longer exists today. The traditional wooden architecture of Northern Vietnam that is still popular today is the architecture of the traditional beam or overlapping beams, overlapping beams with gong prices, dating back earliest from the Mac dynasty (16th century) to the Le Trung Hung dynasty (17th-18th century), and the most popular was the Nguyen dynasty (19th century) (Vu Tam Lang, 2010). Therefore, it is difficult to access this document to study and decode the palace architecture, because it is religious architecture, folk architecture, not royal architecture. Interestingly, among them, we still see some remaining types of dove-beam architecture even though it dates later than the early Le Dynasty and it has been mixed with traditional stacked-beam architecture. These are the bell tower architecture of Keo Pagoda (Vu Thu, Thai Binh), Tay Dang Communal House (Ba Vi, Hanoi), the Holy Temple of Boi Ke Pagoda (Thanh Oai, Hanoi) and some remaining dove-beams at Kim Lien Pagoda (Ba Dinh, Hanoi), Dong Ngo Pagoda (Thanh Ha, Hai Duong) (Figure 5) or the altar of Ba Tam Pagoda (Gia Lam, Hanoi) (Figure 10). These rare images are considered to be the remnants of dove-beam architecture, authentic evidence of the existence of dove-beam architecture in the history of Vietnamese architecture (Bui Minh Tri, 2019). In some previous research works, through observing the roof structure of the upper hall of Dau Pagoda (Bac Ninh), Thai Lac (Hung Yen), Boi Khe (Ha Tay) and based on the architectural model documents of the Tran Dynasty discovered in Nam Dinh and Thai Binh, Trinh Cao Tuong and Ha Van Tan have speculated about the existence of dou cong in Vietnamese architecture of the Tran Dynasty (Trinh Cao Tuong, 1978; Ha Van Tan - Nguyen Van Ku - Pham Ngoc Long, 1993). However, due to the lack of sources, researchers have not been able to discuss further about the structure and form of dou cong in the context of contemporary Vietnamese architecture. Researching the history of Chinese architecture, we know that dou cong is a type of roof support structure using the technique of overlapping beams, located under the eaves and roof. It has the effect of expanding the area of the porch, has the ability to withstand force and acts as a decorative detail to create beauty for the building. By assembling many rectangular wooden frames, the dou gong can transfer the extremely large weight of the roof to the supporting columns, helping the architecture stand firm and not shake when an earthquake occurs. With this structure, the dou gong also has the ability to reduce the impact of earthquakes on buildings, minimizing damage to structures when an earthquake occurs (Duong Hong Huan, 2001; Luu Suong 2009; Phan Coc Tay and Ha Kien Trung, 2005). This is a very meaningful observation when studying the history of Vietnamese architecture as well as ancient architecture in East Asian countries. Historical facts have proven that, although the dou gong has decorative elements, the load-bearing structure of the dou gong architecture is very clear, especially its ability to minimize damage to structures when an earthquake occurs. This can be seen through the longevity of many Japanese and Chinese fortifications that have withstood many major earthquakes and tsunamis that occurred in history and in recent years. Vietnamese historical records also contain records of earthquakes that occurred in the history of Northern Vietnam, including the Thang Long Capital area. Based on statistics from the Complete Annals of Dai Viet, woodblocks carved in the 18th year of Chinh Hoa (1697), we have compiled 39 earthquakes that occurred from the Ly Dynasty to the Mac Dynasty, of which the most occurred during the Ly Dynasty (20 earthquakes), the Tran Dynasty (10 earthquakes) and the Early Le Dynasty (6 earthquakes). It is noteworthy that historical records record damage to animals, trees, and crops, but do not record damage to houses, nor do they mention the collapse or damage to palaces in the royal palace (Complete Annals of Dai Viet, 2011). This leads to the speculation that the wooden structures in the royal palace could still survive strong storms and earthquakes. This is an extremely interesting issue for the journey of decoding the type of dou-cong architecture in the history of Vietnamese architecture. For the early Le Dynasty, in terms of archaeological documents, we have much better opportunities than the documents of the Ly and Tran Dynasties. This period has drawings of dou-cong architecture described quite vividly with many roof levels inside a large ceramic plate of the early Le Dynasty (see Figure 6); the types of dou-cong systems, especially the red-gilded vases in the dou-cong system, were excavated at Area AB of the relic site 18 Hoang Dieu (west of Kinh Thien Palace) in 2002-2004. These are the first and important archaeological clues that suggest a direction for research on the roof support frame system of the palace architecture of the early Le Dynasty (see Figure 7cd). Excavations around the Kinh Thien Palace area in 2017-2018 also found 70 wooden architectural components, including columns, corner beams, porch rafters, floorboards, roof beams on the truss system... located at the bottom of a Le Dynasty stream. Notably, when approaching the research, we determined that there were quite a few components in the structure of the truss system, which are the types of "ang vases" mentioned below. This document clearly proves that the architecture of the early Le Dynasty also belonged to the type of truss architecture (Bui Minh Tri, 2021).

The roof morphology and the structure of the main altar in the Mac Dynasty, 16th century, Ba Tam Pagoda, Gia Lam, Hanoi (left photo), The blue glazed architectural model depicts in detail the main altar structure in the early Le Dynasty, 15th century, found at the east of Kinh Thien Palace (right photo) (Source: Bui Minh Tri).

The rarest image that quite realistically describes the type of dou-cong architecture in the early Le Dynasty is the drawing inside the large 15th century disc as mentioned above. Inside this disc is drawn the image of 5 dou-cong architecture with two roofs (double-roof) and a "side-gable" roof. This is considered extremely important evidence reflecting the existence of the dou-cong architecture in the history of Vietnamese architecture in the early Le Dynasty (see Figure 6). Up to now, the Thang Long Imperial Citadel relic site has found parts or wooden structures related to the dou-cong of the palace architecture in the early Le Dynasty, which are: Dou and various types of vases, but the dou-cong (or dou-cong arms) and the lu-cong have not been found (see Figure 7). Although the complete components of a dou-cong system have not been found, in the light of this authentic document, it has promoted the direction of academic research on dou-cong architecture in the early Le Dynasty. According to the common concept, a dou-cong consists of two components, which are the dou and the buttress. However, the structure of a “dou-cong system”, “a set of dou-cong” or “a group of dou-cong” is much more complicated, consisting of many components linked together, including types of dou-cong, types of buttress and types of slats. The first wooden component related to the dou-cong during the early Le Dynasty was found in a hole dug in the riverbed in the middle of the AB area at 18 Hoang Dieu, which was a small square dou-cong. This type of dou-cong was painted red, measuring 13.5x13.5cm, 6.0cm high, with an oval mortise hole at the bottom, a groove on the surface to support the buttress arm 7.5cm wide, with 2 small square grooves on both sides, if viewed from above it has a horizontal H shape. In the Chinese Ming Dynasty, this type of dou-cong structure was quite popular, called Qixin-dou (齐心斗) or Xuyen tam-dou or Dong tam-dou (Luong Tu Thanh, 2006) (see Figure 7d). The difference is that the Vietnamese dou-cong legs are often evenly curved, not 60-degree diagonally beveled like the Chinese types of dou-cong. The second component related to dou-cong is the Ang type (according to the pronunciation of Doanh tao phap thuc). Based on the drawing in the original Doanh tao phap thuc, the wooden components in the dou-cong cluster with the socket facing up are all classified as Cung type. And the wooden components in the dou-cong cluster if the socket facing down are all classified as Ang (Luong Tu Thanh, 2006). Accordingly, the short wooden bars with the socket facing down excavated in the area east of Kinh Thien Palace are all called Ang, and belong to the Binh Ang type, that is, the horizontal Ang type, distinguished from the diagonal Ang type. This type of vase has many different lengths and shapes, including 3 main types: vases with 5 grooves, vases with 3 grooves and vases with 1 groove. Vase with 5 grooves: There are 3 that are still in their original shape, both ends are shaped like cloud patterns, so they are called cloud-headed vases. This type of vase is 132cm long, 11cm thick and 15cm high (see Figure 7a). Vase with 3 grooves: There are 2 that are still in their original shape. The first one has a triangular obtuse angle at the top, looking like a grasshopper's head, so it is called a grasshopper-headed vase. This type of vase is 96cm long, 8.0cm thick and 13cm high (see Figure 7b). The second one has both ends shaped like cloud patterns like the vase with 5 grooves mentioned above, so it is called a cloud-headed vase. This type of vase is 113cm long, 11cm thick and 15cm high. The vase has 1 groove: There are 2, both are broken or burned, only the head remains, the remaining size is about 67-76cm long, 6.5-7.0cm thick, 12.5cm high. This vase has a long head that curves downwards like a bird's beak, so it is called a bird's head vase. This type of vase is very popular in China, it appeared from the Song Dynasty to the Ming - Qing Dynasty and there are 2 main types: medium vase and low vase. Medium vase usually has 3 grooves, low vase usually has 1 groove. The vase found at 18 Hoang Dieu belongs to the 1 groove type (see Figure 7c). Thus, the vases found at the Thang Long Imperial Citadel are mainly the type with odd number of grooves: 1 - 3 - 5, the type with larger number of grooves or the type with even number of grooves (4 - 6) have not been found. This discovery suggests that Thang Long's dou gongs are simple, possibly with 3 or 4 dou gong levels and the size of the dou gong clusters is similar or slightly smaller than the dou gong clusters of China during the Ming Dynasty, through comparison with the Dai Cao Huyen Dien. Research comparing with the dou gong structure of the Dai Cao Huyen Dien during the early Ming Dynasty in the Forbidden City of Beijing (China), the type of vase with 5 grooves is the type of vase located on top of the dou gong cluster, with the function of locking the head of the dou gong cluster; the type of vase with 3 grooves is usually located in the middle of the dou gong cluster; the type of bird head vase with 1 groove is usually located at the bottom and placed on the burner. For ease of reference, we use the terms: Upper Flask for the top type of scuttle (5 grooves), Middle Flask for the middle type of scuttle (3 grooves) and Lower Flask for the bottom type of scuttle (bird-head scuttle with 1 groove) (see Figure 7-9).

Base and beams are removed, the wood is painted and gilded with decorative patterns (Source: Bui Minh Tri)

Despite having gone through many layers of time, the above wooden structures still retain traces of red gilding and real gold plating on the decorative motifs. This vividly reflects that the wooden architecture of the Early Le Dynasty was painted bright red and the decorative motifs were also covered with real gold, creating a colorful beauty for the structure. It is noteworthy that in addition to discovering a series of wooden structures related to the above-mentioned dou-cong architecture, the excavation of the East of Kinh Thien Palace in 2021 fortunately found a very unique green glazed architectural model (see Figure 11). This is the first and only model currently dating from the Early Le Dynasty found in Vietnam. This model depicts quite realistically the roof of the structure covered with smooth tube tiles, with a frieze of water-cutting cau-dao tiles and the structure's frame is a dou-cong system. This is a "linked brace" type of brace, which means that the brace is shown horizontally with high density and the brace is not only arranged on top of the columns but also arranged in the position between the columns or between the compartments (between-compartment brace). Each brace cluster on the model is described quite realistically, including a brace, a brace placed on the brace arm, a bird's head brace, a locust head brace, especially the brace head locking brace placed on the column head is shaped like a protruding dragon head. Comparative research with Chinese brace shows that this is a "cross-brace" type, which is a type of brace combined with a horizontal brace placed on the corner column head to both support the eaves to extend out and support the corner column to bear the load. The brace combinations or brace clusters are placed in many positions in the house frame and extend to four directions. At the roof corners, the braces are deployed systematically in all three directions: the porch corner, the horizontal surface and the gable surface of the architecture. The technical term for this is “three-pole-pole construction”, which means the form of three-pole-pole construction in a horizontal direction (Tomoda Masahiko, 2017). The type of pole construction on this model has many similarities with the wooden altar of the Mac Dynasty, 16th century, at Ba Tam Pagoda (Gia Lam - Hanoi) (see Figure 10-11). This lacquered wooden altar and the above-mentioned blue-glazed terracotta model are considered very rare and valuable sources of information, providing many reliable and authentic scientific bases for research and decoding of the structure of the roof support frame and architectural form of the early Le Dynasty. From the results of the study of drawings, models and wooden pole construction components excavated at the site, it can be said that the pole-pole architecture of the early Le Dynasty has a similar structure to the pole-pole model of the Ly and Tran Dynasties, but has a quite important difference, which is the appearance of “vase” (Bui Minh Tri, 2019). Comparative research on the “vase” in the dou cong cluster of the early Le Dynasty shows that it has many similarities with the palace architecture style of the Forbidden City of Beijing (China) during the Ming Dynasty, such as the case of Dai Cao Huyen Dien. And, it also has quite a few similarities with the dou cong cluster in the architecture of the Back Palace of Boi Ke Pagoda (Hanoi), the bell tower architecture of Keo Pagoda (Thai Binh), especially the architectural model on the wooden altar of Ba Tam Pagoda (Hanoi). Based on this reliable source of information, we have researched and drawn a 3D reconstruction of the dou cong structure of the early Le Dynasty architecture. Interestingly, when studying the shape, size, and groove-making technique of the vases excavated in the East of Kinh Thien Palace and on the basis of comparative research on the types and functions of the vases in the dou cong clusters of the Dai Cao Huyen Dien architecture, we have assembled 3 types of vases into a complete dou cong cluster (see Figure 8). This suggests that the excavation pit area has found parts or components of a contemporary wooden architectural work. Looking at it in the light of this document, and putting it into a dialogue with the wooden architectural styles and the history of ancient palace architecture in the Forbidden City of Beijing (China) during the early Ming Dynasty, we have discovered many interesting things about the dou gong structure between the two dynasties, specifically as stated below. Firstly, the dou gong cluster at the Kinh Thien relic has a structure of 3 slabs and 3 dou gong floors, in which the bird head vase is placed on the dou gong order, similar to the dou gong cluster of the Loi Dai tower architecture (3 floors) located in the complex of Dai Cao Huyen Dien or the water pavilion architecture of Ha Nam (China) (see Figure 9). Evidence from the architectural model excavated at the site and the style of the wooden altar in the Mac Dynasty at Ba Tam Pagoda also suggests that the wooden altar in the early Le Dynasty may have had a fairly simple structure, consisting of 2 floors and 1 floor, in which the bird's head vase was placed on the order (see Figure 10-11). However, comparative research with the main hall architecture at Dai Cao Huyen, the wooden altar in the Mac Dynasty led to the speculation that the Kinh Thien Palace architecture had 2 roof floors (double roof), equivalent to 2 floors of the altar. According to the theory of Doanh Tao Phap Thuc and comparative research on the structure of the main hall of Dai Cao Huyen, the lower and upper altar floors are often different, the upper floor is one floor higher than the lower floor. Specifically, in the case of Dai Cao Huyen, the lower altar floor of the lower porch has a structure of 3 floors, 3 floors of the altar and uses a single bird's head vase (ha ang) placed on the order. The upper porch has a structure of 3-beam and 4-beam, in which the armrest (flower-beam) is placed on the incense burner, in the middle are 2 bird-head vases (central beam). From this model, we assume that the architecture of the Early Le Dynasty may have a similar structure to the Dai Cao Huyen Palace (see Figure 9). This is a rather important issue in determining the height and width of the porch as well as the class of the building.

Research on decoding the function of wooden architectural components in the early Le Dynasty (Source: Bui Minh Tri)

Second, although there are similarities in type and structure, the details of shape and form show that the architecture of Vietnamese and Chinese dou gongs have very different points. In particular, based on the documents from the architectural models excavated at the site, we can see a quite interesting difference between Vietnamese and Chinese dou gongs, which is the appearance of dragon heads protruding from the heads of the vases on the top floor of the dou gongs. This form can also be seen in reality in the architecture of Tay Dang communal house or Boi Khe pagoda. However, the dragon heads on the vases of these architectures are often placed facing inside the house (see Figures 5.1, 5.3). With the palace architecture of the early Le Dynasty, research from the terracotta model documents shows that the dou gong cluster with the upper vase decorated with dragon heads is often placed on the top of the columns, while the dou gong cluster with the upper vase decorated with cloud patterns is often located between the columns or between the compartments (dou gong between compartments). This is a distinctive feature, a unique feature of Vietnamese palace architecture during the early Le Dynasty. In addition to the above archaeological documents, in the excavation pit east of Kinh Thien Palace, at the same location where the vases were discovered, corner beams, porch rafters and upper beams were also found. Considering the context of discovery and research on type and function, we determined that these are important components related to the structure of the roof support frame and the roof morphology of the dou-cong architectural work (see Figure 12-13). Corner beams are components placed at the roof corners of the work, with the function of raising the height of the ridge and creating a curve for the roof corner. In the excavation pit east of Kinh Thien Palace, the 2018 excavation was fortunate to find a relatively intact corner beam. The beam was made from a rectangular block of wood 16cm thick and 238cm long. The beam head is beveled at a 48.2 degree angle, 27.5 cm high, the long body has a raised edge in the middle and is curved like a boat's bottom, gradually narrowing towards the back. The two sides and the front end are painted with red lacquer, the head is carved with cloud patterns and painted with soft borders in real gold. There is a mortise hole on the head, between the body and the head there are 2 mortise holes to connect with the upper and lower structures to create stability and raise the height of the roof angle (see Figure 12a). The eaves are the type of structure used to support the roof in the eaves and create the width (overhang) of the eaves. In the same area where the corner beam was discovered, a number of eaves were found, most of which were broken, leaving only the head, including one that was quite intact, 140 cm long and 11.5 cm thick. The rafters have a round head (5cm in diameter), are 45cm long and have a 21.5 degree bevel, the body is a flat rectangular block, tapering towards the tail. On the body there are 2 small rectangular mortises to connect with the crossbar below. The rafters' heads are painted red, the body is left with natural wood (see Figure 12b). Based on the red lacquer characteristics at the rafters' heads, it can be inferred that the rafters of the early Le Dynasty architecture would be exposed, under the tiled roof, the rafters can still be seen protruding like the rafters of the palace architecture of China, Korea and Japan. This also means that the rafters of the early Le Dynasty architecture do not use roof rafters to cover the rafters (see Figure 13). This is a distinct feature from the architecture of the Ly and Tran dynasties (Bui Minh Tri, 2019). The appearance of the truss structure and the use of rafters on the porch with the above characteristics shows a very clear change in style of the palace architecture of the early Le Dynasty compared to the palace architecture of the Ly and Tran Dynasties. The upper beam is a horizontal beam-shaped structure located on top of the roof truss of the building. Because its cross-sectional shape resembles a crescent moon, it is also called a moon beam. In the area east of Kinh Thien Palace, a wooden structure of this type was excavated. Although one end was broken, it can still be recognized as an upper beam because it has a round body, a curved belly, two square ends with a mortise and tenon facing down, the remaining length is 227cm, 30cm high and 22cm thick. The mortise and tenon at both ends shows that it was placed on the top of a short column (hidden column) standing on a wooden beam. On the back of this structure, there are 2 mortise holes to place an additional corner beam overlapping on top to support the roof beam. Based on this clue and the study of the truss structure of the Tran Dynasty at Thai Lac Pagoda (Hung Yen), Dau Pagoda (Bac Ninh) or Tay Dang Communal House (Hanoi) during the Mac Dynasty, it can be inferred that the truss of the architecture of the early Le Dynasty may have had a structure of overlapping beams. This is the traditional truss style of Vietnamese wooden architecture (see Figure 14). This discovery also suggests that the truss architecture of the early Le Dynasty may have had a clever combination of "clusters of trusses" on the porch and the "overlapping beam" roof truss system above the trusses.

Structure of the trusses of Thai Lac Pagoda (Hung Yen) and Dau Pagoda (Bac Ninh) during the Tran Dynasty, 13th - 14th century (Source: Tran Trung Hieu - Institute of Monument Conservation, 2018)

It can be said that the architectural drawings on exported ceramics and archaeological discoveries of wooden components of the dou-cong architecture and the dou-cong architectural model are reliable scientific bases for the assertion that the palace architecture of the early Le Dynasty was dou-cong architecture. In the context of the research on the history of ancient Vietnamese architecture, which still has many large gaps, this is a very important assertion, the key to decoding the architectural form of Kinh Thien Palace. The results of this research contribute to clarifying the history of palace architecture in the Thang Long Imperial Palace, further consolidating the assertion: The palace architecture in the ancient Thang Long Imperial Palace (from the Ly, Tran to Le dynasties) was popular or mainly dou-cong architecture (Bui Minh Tri, 2021). From the above research results, combined with comparative research with the architecture of Dai Cao Huyen Dien and Thuy Dinh in Ha Nam (China) in the early Ming Dynasty and the architectural relics of the Vietnamese Dou Cong in the Mac Dynasty and the Le Trung Hung Dynasty, we have a completely reliable scientific basis for recreating the image of the roof support frame of the palace architecture of the early Le Dynasty, especially the architecture of Kinh Thien Palace (see Figure 15b). On the other hand, as mentioned above, on the wooden structures excavated at the relics, there are still traces of red and yellow gilding on the decorative motifs. This evidence reflects that the Dou Cong clusters and architectural frames of the early Le Dynasty did not keep the original wood color but were all painted red and real gold was used to paint on the decorative motifs (see Figure 13). This leads to the conclusion that the palace architecture of the Early Le Dynasty was designed very elaborately, decorated elaborately and magnificently with many splendid and luxurious colors, with a beauty similar to the most famous palaces in East Asia at that time. In the palace architecture in Beijing (China) or Changdeokgung (Korea), the wooden frame of the building, especially the girder system, was commonly painted with vermillion and painted with patterns in many different colorful colors, creating the splendid and noble beauty of the palaces in the royal palace, demonstrating the power, authority, wealth and prosperity of the dynasties.

Comparison of truss structure of Vietnamese architecture in the early Le Dynasty (Kinh Thien Palace) and Chinese architecture in the Ming Dynasty (Dai Cao Huyen Palace) (Source: Ngo Vi - Bui Minh Tri - Nguyen Quang Ngoc)

Another interesting point when studying the decoding of the roof support frame is that we also need to study the truss structure of the building, that is, study the interior structure of the building. But this is a very difficult problem because when studying on models, we only know the external shape of the building, so the internal structure of the building is still a mystery. Field studies of palace architecture in China and Korea show that inside the palaces there are often ceilings to hide the structural features, so the roof support frame and truss of the building are not visible. Only by studying the drawings can we know that the truss structure of these buildings is commonly the "dove-beam-stacked-beam" style, and the structural components are often not carved with decorative patterns (see Figure 15a). In contrast, the interior of traditional Vietnamese wooden architecture is often not ceiling-shaped but is a place for architects to show off their ingenuity in carpentry as an artistic creation, so that the entire truss system and the structure of the roof support frame can be seen. With this feature, the truss system of Vietnamese architecture is often carved with elaborate patterns, creating beauty for the interior of the building. The decorative wooden components of the Tran Dynasty on the remaining trusses at Thai Lac Pagoda (Hung Yen), Dau Pagoda (Bac Ninh) or later at Tay Dang Communal House (Hanoi) during the Mac Dynasty are important suggestions about the structure and carved decorations on the trusses of contemporary wooden architecture (see Figure 14). The discovery of the "upper beam" structure of the truss system in the overlapping beam style at the East of Kinh Thien Palace mentioned above suggests that the architecture of the early Le Dynasty may also have a quite delicate and harmonious combination of the "dau cong - overlapping beam" style (see Figure 15b). This is a very interesting issue that needs further research in the future.

Source: https://danviet.vn/dien-kinh-thien-thoi-le-so-loi-kien-truc-doc-dao-hoang-cung-thang-long-xua-cung-dien-co-do-so-20241203165715798.htm