The ruins of the Church, started toward the year 1000 by the benedictines and finished toward the end of the XII century, consist in the apse, in the eastern walls of the transept and in the arches which support the dome with the plumes from which developed the octagonal dome and you set yet the base of the lantern. The beautiful capitals of semipilastri, decorated with leaves and anthropomorhic heads, were approached to those of San Rabano common in derivation of models of the Alps.
The apse has an elegant decoration to hanging arches divided for couples by slender semicolumns. The perfect embodiment of the curtain wall outside, large ashlars of travertine perfectly squared, contributes to value also the appearance of ruin.