Corner towers 角樓 on the four coigns of the lofty palace walls were established in 1420, rebuilt in the Qing Dynasty (1644-1911). As one part of the Forbidden City, they served as the defense facility just as the lofty walls, the gate towers and the moat.
They rest on the base with Buddist-style building surrounded with stone columns. There goes a tale about the construction of them. Zhudi 朱棣, Emperor Yongle of the Ming Dynasty, ordered the chief project commander to build four fine corner towers, each with 9 girders, 18 posts and 72 ridges 9梁 18柱 72脊. The chief project commander gathered all the foremen and carpenters and gave them three months to fulfill the mission. This was an impossible task as nobody had ever built such a complicated yet delicate corner tower. Deep in worry, a carpenter met an old man selling grasshoppers and bought a grasshopper cage for relief. To his surprise, the delicate grasshopper cage with layer upon layer had just 9 girders, 18 posts and 72 ridges. Thereafter the design was brought out. It is said that the old man was the Master of the builders, Luban 魯班.
This is definitely nothing but a tale. However, the four of the Forbidden City inherited the flexibility of the traditional wood structure construction and the skilful combination of the function and decoration indicated the superb and excellent craftsmanship of ancient Chinese craftsman.
Gallery of Historic Architecture
The Gallery of Historic Architecture in vicinity of East Prosperity Gate occupies four major sections: the city wall between the Meridian Gate (午門) and the East Prosperity Gate, the southeast corner watchtower 東北角樓, the East Prosperity Gate, and the area around the office of Imperial Procession Guards (鑾儀衛). The city wall section does not house exhibitions but serves as the major passageway between the historical buildings and the key venue for outdoor displays. The corner watchtower is the home to the themed exhibition “Timber Structures of Historic Architecture”, featuring such contents as multi-media productions, architectural drawings and charts (with a three-sided cone rotating display fixture), the main structure and model of the watchtower.
The exhibition gallery at the East Prosperity Gate 東華門 hosts the special exhibition “Ancient Architectural Designs”, consisting of four units: “Planning and Design”, “Interior Decoration and Design”, “Tilework and Design” “Colored Painting and Design”. The exhibition gallery in the Office of the Imperial Procession Guards has the themed display “Masonry and Preservation of Historic Architecture”, including warehouse-style exhibition area for stone relics, conservation studio for stone relics and a service area for the public.