ARCADE, in architecture, a series of arches assembled in a single composition, particularly when the arches are of approx imately the same size and placed upon the same level. Arcades are used structurally as in the arcade between the nave and aisles of a church, which supports the clerestorey wall and the nave roof. They are also used, purely decoratively, where a band of horizon tal decoration is required. Although the arch was known to many of the peoples of antiquity, it was the Romans who first appre ciated its decorative possibilities and who made it, again and again, a dominant feature of great architectural importance, as in the Tabularium (q.v.) and in any Roman amphitheatre. An arcade, such as those used by the Romans, with the front face of each pier ornamented by a pilaster or engaged column that carries an entablature running over the tops of the arches, is known as a Roman arcade, and was a favourite motive of the Renaissance. During the late Empire, the Romans started to build arcades whose arches were carried directly upon the capitals of a range of columns (e.g., the great court of the palace of Diocletian at Spalatro), and during the Romanesque and Gothic periods this became the normal type, although in the Byzantine work of the eastern empire, spreading blocks, known as impost blocks, were often placed between the capitals and the arches.
Arcades were used decoratively, to a great extent, in north Ital ian Romanesque. Some fronts, such as that of the cathedral at Pisa, consist entirely of rows of freestanding arcades. In the mediaeval architecture outside Italy (except for the Romanesque churches on the Rhine, where Italian influence is strong) deco rative arcades were almost always actual parts of the wall and are known as wall arcades.
Interlacing arcades are those in which every arch spans the space, not to the adjacent support, but to one of those beyond. All of the arches are of the same size and, therefore, apparently over lap or intersect each other. They form a favourite motive for the decoration of walls, both exterior and interior, in the Romanesque work of northern Europe generally and the Gothic of England. The word arcade is also used, at the present time, to designate any covered passageway on which shops open. (T. F. H.)