QUADRIPORTICO. — Varro, in “De Lingua latina” (V, 161), specifies the distinctive function of the atrium or q. as an environment “qui esset ad communem omnium usum.” In substance, this function always remained, and this explains its adoption in the architectural complex of the Christian basilica.
The q. of the great basilicas was enclosed on all four sides by colonnaded porticoes; it could be built directly against the façade, or communicate narthex (v.), and, in the absence of the latter, served to receive penitents and catechumens. At the center stood a large basin (cantharus), for the purifying ablutions of the faithful before entering the church; as Eusebius attests (Hist. eccl., X, 4, 1) in the case of the basilica of Tyre, the fountain was considered indispensable, and in the ancient S. Pietro in Vaticano it was sometimes covered by a canopy supported by four columns or protected by enclosures. This original character of the q. soon declined into the humbler function of shelter for pilgrims and place of burial: correspondingly, it acquired the more noble appellation of paradisus. Later, in Rome and elsewhere (S. Clemente, S. Maria in Cosmedin, S. Frassede; Cimitile near Nola, etc.), in place of the usual arch or vaulted entrance through which it communicated with the street, there appears a small structure supported by columns, the so-called prothyrum. In the East, sacred architecture preferred the narthex alone. With the spread of monasticism, new spaces were built onto the rear of the church, and, in order to isolate the community, the center of the cenobium, with its well or fountain recalling the fountain of the q., was preferred (v. CHIOSTRO). The atrium, however, did not disappear entirely: from S. Ambrogio in Milan (11th century) to S. Maria de’ Pazzi in Florence (15th century); from S. Gregorio al Celio in Rome (17th century) to the Ostian basilica of S. Paolo, reborn after the fire; the q. has survived in the taste of art, perhaps because its welcoming silence and shadowy recesses invite the soul to recollection and prayer.
della genesi della basilica crist., in Atti della Pont. acc. rom. di archeol., 2ª serie, 15 (1921), pp. 111-34; G. M. Kaufmann, Handbook der christl. Archäol., 3ª ed., Paderborn 1922, p. 156 ff. Pasquale Testini