It was built around the middle of the 5th century, at the behest of Galla Placidia, who ruled the Western Roman Empire. This small Latin cross mausoleum, externally is very simple, while inside it has a rich mosaic decoration. The countless stars of the dome have struck the imagination and sensitivity of visitors over the centuries, as well as outstanding personalities such as the great poet Dante Alighieri, who drew inspiration from them for the drafting of some verses of the Divine Comedy.

It is one of the most important monuments of early Christian art in Italy. The monument is of the sixth century, of clear eastern influence, it has an octagonal plan, surmounted by a large frescoed dome. When one enters the basilica, the gaze is captured by the high spaces, the stupendous mosaic decorations of the apse, and the extraordinary representation of the imperial couple from Byzantium, Giustiniano and Teodora, with their parades.

One of the oldest monuments in the city, in simple brick on the outside but rich in marble, stucco and mosaics with a clear Hellenistic-Roman influence on the inside. Dominating the dome, commissioned by Bishop Neone in the mid-fifth century, is the scene of the Baptism of Christ surrounded by a very refined procession of the twelve Apostles that stands out against a brilliant background of blue tesserae. Inside there is still the baptismal font from the Renaissance period, which takes up the octagonal shape of the Baptistery plan and which preserves the ambo from the 5th century.

(visit independently) which houses the Chapel of Sant'Andrea: depicting the glorification of Christ in an anti-Arian key, the only example of an early Christian archiepiscopal chapel still intact today