Dome

Dome, in architecture, oval or hemispherical vault, used to roof a large space without interior supports. The first domes were built around 1000 B.C. by the Persians and Assyrians, but these were small, and the dome did not become architecturally significant until the time of the Romans. The Pantheon in Rome (2nd century A.D.), in which the dome rests on a drum-shaped building, is an outstanding example of the large-scale dome. The Byzantine architects of Hagia Sophia (A.D. 532–537) in Constantinople developed the pendentive, a device enabling the construction of a great dome over a square central area. Brunelleschi's dome on the cathedral in Florence has an inner and an outer shell; Sir Christopher Wren's dome for St. Paul's, London, has 3 shells. Modern techniques and lightweight materials permit the spanning of vast areas, as in the case of the Houston Astrodome.

See also: Architecture.