DOOR. – In antiquity, alongside the monumental type, already present in Egyptian and Assyrian civilization, which in the imperial age would develop into the great archways at the entrances to Italic and provincial cities, there persisted the type of door with a clearly rectangular opening, framed by a band and surmounted by a high frieze. The first Christian basilicas drew inspiration from this type, when the absence of a narthex or atrium did not interfere with the door’s essential function. In the door of S. Salvatore in Spoleto (4th century), even the decorative elements recurring in the framing belong to the Roman tradition.
Given the poverty of façades in the Byzantine age, the door was reduced to the simplest form, often merely a projection of the wall surface. The classical tradition, however, persisted longer in Rome, also because of the abundance of classical ruins there, from which it was possible to recover fragments of friezes and architraves for decorative purposes. The disappearance of this practice after the 7th century coincided with an impoverishment of architectural forms, so that the door remained of an extremely simple type, either with an architrave or arched, frequently employing a relieving arch. The entrance to the chapel of S. Zenone in the church of S. Prassede, flanked by two ancient columns on which a classical architrave is set, bears witness in the first half of the 9th century to a return to the serenity of ancient structural rhythms.