ATRIUM (Atrion, Aidrion). - In the Christian architecture of the early centuries it consists of an open space placed directly in front of the church's facade and surrounded by porticoes that bound its quadrangular area. The porticoes of the atrium occupy the entire front of the church and are not extremely visible, because they are enclosed by a continuous wall, interrupted only by the openings for the doors. The roofing of the porticoes is supported by these perimeter walls and, toward the inside, by free-standing columns, arranged parallel to the boundary walls and equally spaced.
The diffusion of the atrium is characteristic, if not exclusive, of the Christian West: in Rome it characterized all the major basilicas. For this reason too, the formal analogies that the atrium of the early Christian church presents with respect to that of the Roman house therefore appear evident. The atrium was also customarily called paradisus (whence the French word pareis), perhaps because it was often laid out as a garden, or in Greek αὐλή. It preceded the narthex (v.) and extended on three sides (triporticum) or, more often, on all four (quadriporticum). A fountain in the middle, more commonly called cantharus (v.), served for the ablutions.
The ritual purpose of the atrium is illustrated by the sacred writers, as a place initially intended to gather the catechumens and the penitents; its purpose therefore corresponded precisely to the architectural function of an intermediary element, intended to separate the sacred building from the public streets, thus removing it from profane outer life. This same purpose, on the other hand, was more often achieved in the East by adopting the peribolos (v.).
Around the 7th century, as the liturgical reasons for which it had been created fell away, the atrium tended to diminish in importance and then to disappear; nevertheless, we still see it occasionally realized, in pre-Romanesque and Romanesque churches, as in the well-known examples of the basilicas of St. Clement in Rome, St. Ambrose in Milan and the cathedral of Salerno. One can also discern a derivation of it in monastic cloisters which, presenting the same ground plan arrangement, were very probably modeled on the atrium of the early Christian church, though deprived of its specific function. Also in the Renaissance (the churches of the Santissima Annunziata and of Santa Maria Maddalena dei Pazzi in Florence, of St. Gregory on the Caelian in Rome) the atrium is sometimes placed in front of churches with an ever-increasing variety of adaptations, so much so that in current usage the term also denotes the simple portico or any space that precedes the hall of churches. - See Pl. XXVII.
