It has a Roman cross plant, divided into three naves with a transept and a semicircular apse. The roof of the nave is a wooden trusses, while the crossing of the transept is covered by cross vaults. The outer walls are made of tufa, the floor in marble. Church belongs to the twelve-sided tower. Inside there are a Cosmatesque pulpit, newsstand tomb, the remains of a body of paintings including works dating from the '300 to' 600, to the 800. In the crypt are visible remains of the previous phases of use of the complex, which is a place of worship since the Villanovan period. The most notable is the upper layer, in which are preserved remains of extensive floor mosaics belonging to the twelfth century.