Caisson (Asian architecture)

The Caisson (Chinese: 藻井; pinyin: zǎojǐng; literally: "algae well"), also referred to as a caisson ceiling, or spider web ceiling, in East Asian architecture is an architectural feature typically found in the ceiling of temples and palaces, usually at the centre and directly above the main throne, seat, or religious figure. The caisson is generally a sunken panel set into the otherwise largely flat ceiling. It is often layered and richly decorated. Common shapes include square, octagon, hexagon, circle, and a combination of these.

The caisson is a general name for a coffer. In the case of East Asian architecture, however, the caisson is characterised by highly developed conventions as to its structure and placement.

The caisson is a sunken panel placed in the centre of the ceiling. It is raised above the level of the ceiling through use of the dougong (斗栱) structure, which, through interlocking structural members, as beams were not used, creates successive levels of diminishing size. Beams may also be used to create a hexagonal or octagonal caisson surrounded by a square border. These beams, and the dougong members, are usually visible, and richly carved and often painted with deities.

The centre of the caisson is decorated with a large bas-relief carving or painting. Common themes include "two dragons chasing the pearl". Caissons in the throne rooms of the Forbidden City feature a large, writhing dragon, from whose mouth issue a chandelier-like structure called the Yellow Emperor Mirror, a series of metal balls which are said to be able to show reflections of evil spirits.

Caissons were originally used to support skylights. Therefore, they are a relatively recent structure in the Chinese architectural history. However, they became increasingly intricate and formalised, and were in later periods a standard item of interior decoration in formal buildings.

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