baldachinum

[altar canopy]A dome-like canopy in wood, stone, or metal erected over a high altar, either supported by columns or suspended by a chain; also known as a ciborium. It originated in the altar-canopy, a square covering suspended over the altar to protect it from dust or material falling from the ceiling. The most notable example is that of Saint Peter’s in Rome, Italy designed by Bernini for Pope Urban VIII. The name is derived from Baldocco, the Italian form for Baghdad, whence came precious materials used for these canopies. The term is also applied to movable canopies which are used in processions or to those placed over an episcopal throne.