Cupola

A spherical ceiling, or a bowl-shaped vault, rising like an inverted cup over a circular, square, or multangular building or any part of it. The term, properly speaking, is confined to the under side, or ceiling, of a dome, and is frequently on a different plane from the dome which surrounds it outside. It is also sometimes applied to the dome (but for this there is no authority), and to a small room, either circular or polygonal, standing on the top of a dome, which is called by some a lantern. A cupola does not necessarily presuppose a dome, and the latter is often found surmounting flat surfaces. The significance of the term is in its form and has nothing to do either with the material used or with its method of construction. According to Lindsay, the cupola of San Vitale, at Ravenna, became the model of all those executed in Europe for several centuries. This cupola is of remarkable construction, being built wholly of hollow earthern pots, laid spirally in cement, a light construction common in the East from early times. The cupolas of the Pantheon at Rome, the cathedral at Florence, the churches of St. Peter at Rome, and Santa Sophia at Constantinople are of solid construction, and the support of the cup-shaped vault is either by pendentives or by a drum. In some cases, however, the cupola is of masonry, and the outer shell of the cupola is of wood covered with lead, as at St. Paul's, London, and at St. Mark's, Venice, the five masonry cupolas have the outer shell of wood and metal. The dome of the Invalides, in Paris, has a wood and metal covering above two inner structures of stone. In the later Byzantine buildings of Greece and other parts of the Levant, many of the cupolas have singularly lofty drums, which are pierced with windows, and the cupola proper becomes a mere roof to a tall cylindrical shaft. Cupolas in modern construction are generally of wrought iron, and the space filled in with some tile formation. The term is sometimes applied to a small roof structure, used for a look out or to give access to the roof.