Coffer

A coffer (or coffering) in architecture is a series of sunken panels in the shape of a square, rectangle, or octagon in a ceiling, soffit or vault. A series of these sunken panels was often used as decoration for a ceiling or a vault, also called ''caissons'' ("boxes"), or ''lacunaria'' ("spaces, openings"),).}} so that a coffered ceiling can be called a ''lacunar'' ceiling: the strength of the structure is in the framework of the coffers. Provided by Wikipedia