Basilica of Sant'Ambrogio, Milan
The Basilica of Sant'Ambrogio (basilega de Sant Ambroeus in Milanese dialect), whose full name is the minor Roman basilica, collegiate, abbatial and provostal church of Sant'Ambrogio[1] (original Early Christian name basilica martyrum), is one of the oldest churches in Milan. It stands in Piazza Sant'Ambrogio and is not only a monument of the Early Christian and Romanesque periods but also a cornerstone of Milanese history and of the Ambrosian Church. It is traditionally considered the second most important church in the city after Milan Cathedral. Together with the basilica prophetarum, the basilica apostolorum and the basilica virginum, the basilica martyrum is one of the four Ambrosian basilicas, those built by Saint Ambrose.
Built between 379 and 386, in the late imperial Roman period, at the behest of Ambrose, bishop of Milan, at a time when the Roman city of Mediolanum (modern Milan) was the capital of the Western Roman Empire (a role it held from 286 to 402), it was almost entirely rebuilt, taking on its definitive appearance between 1088 and 1099. The new 11th-century basilica scrupulously retained the plan of the original Early Christian church of the 4th century: three apsed aisles without a transept, preceded by a quadriporticus. The architectural complex comprises the monastery of Sant'Ambrogio, the canonry of Sant'Ambrogio, the church of San Sigismondo and the basilica. It is one of the Early Christian basilicas of Milan.
Artistically notable are the main entrance portal of the basilica, with its meticulous relief decoration; the altar of Sant'Ambrogio, made between 824 and 859 by Wolvinius for the Archbishop of Milan Angilbert II, with a precious gold antependium in relief, set with gems on all four sides; the Ottonian ciborium, resting on four red porphyry columns and bearing stucco high reliefs on its four faces; the apse conch, decorated with a mosaic dating from the 11th century; and the Early Christian shrine of San Vittore in Ciel d'Oro, dating from the 5th century, whose vault is entirely covered in gold leaf. The side walls of the shrine of San Vittore in Ciel d'Oro are covered with a mosaic depicting six saints, including Saint Ambrose; this is the oldest known depiction of Milan's patron saint (Wikipedia).