The Oratory of S. Andrea - Archiepiscopal Chapel was built as a private chapel during the reign of Theodoric, King of the Ostrogoths. Erected by Bishop Peter II the chapel is in the form of a cross with a vestibule fully faced with marble on the lower half and with mosaic decoration on the upper half. It is the only Orthodox monument built during the reign of Theodoric, when the predominant religion was Arian. The mosaics are beautiful, depicting the Glorification of Christ, whose figure dominates every part.