Following a radical renovation in the 13th century, the interior has a single chamber, with a raised presbytery and ends with a deep apse where you will notice numerous fragments of sculptures from the middle ages, re-used in its building. The ceiling is particularly interesting, with wooden beams and painted bricks, and is reinforced by transverse gothic arches. Above the narrow passage that leads to the crypt, to the left of the flight of steps, is an ambo decorated with reliefs. The ambo is made of two big marble slabs that are entirely covered with sculpted bas-reliefs. The resulting effect is particularly notable in the inner slab of the ambo, where the traditional pattern with interwoven ribbons forms large, irregular knots. On the outer slab, which faces onto the nave, the usual iconographic repertoire of Lombardic art, is enriched with flowers, bunches of grapes and other symbolic elements inspired by classical art.
The crypt, datable to the end of the 9th century, is dominated by a large grey marble central column, with an ionic pillar that supports the vault, reinforced with arches during its renovation in the thirteenth century. Along the left-hand side of the church, is the impressive bell tower which rests on a large structure with a large-domed vault of the late Imperial age.