San Vitale, Rome

The early Christian imperial basilica of the Saints Martyrs Vitale, Valeria, Gervasio and Protasio known more commonly as the basilica of San Vitale and Compagni Martiri in Fovea or more simply as San Vitale al Quirinale. It is the oldest Catholic place of worship in the historic center of Rome, located in via Nazionale. The imperial basilica of San Vitale al Quirinale, built under the pontificate of Pope Siricius after 386 and consecrated and richly decorated by Pope Innocent in 402 is the first public Christian basilica with a baptistery not founded on pre-existing pagan temples, mentioned in the Liber pontificalis, built by the Emperor Theodosius at the behest of Saint Ambrose of Milan, in honor of the miraculous discovery of the bodies of martyrs Gervasius and Protasius in Milan. It is the most frescoed basilica in Rome.

Source: Wikipedia