Architecture and Art. In Romanesque style, with the façade and sides in tuff, three naves and three apses, the crypt and raised presbytery, the church was consecrated by the Bishop Ognibene in 1164. The façade has simple lines, with small arches on top, a double lancet window and lateral windows; the door is square and made from reed marble. It dates from the beginning of the XV century. Above the door there is a noteworthy prostyle.
On the right side of the church there is a surviving wall of a beautiful Romanesque cloister and square bell tower, which is Romanesque on the lower part and eighteenth century on the upper part.
Adjacent to the wall of the church and college, there are stems, plaques and sepulchre seals. Inside, the baroque altars of the lower church and the central altar of the upper church are worthy of attention, along with the renaissance baptistery and a St. John, by D. Brusasorzi.
The crypt. Extremely beautiful and recently restored, the crypt occupies the lower space of the church.
The front part is the oldest, dating from the IX century, and has a square floor plan with eight columns, while the rear part is in Romanesque style (XII century) with crossed vaulted ceilings and the traditional three naves.
ON the right hand side, the remains of several seriously damaged frescoes can still be seen. The crypt contains two beautiful sarcophagus of Greek marble from early Christian times. The largest one, according to tradition, contains the relics of Saints Simon and Giuda Taddeo, whose effigies can be seen on cover. The second sarcophagus is decorated with undulated grooves; on the side, Saints Peter and Paul can be seen, while in the middle, on a shell, the half bust depicting two spouses can be seen.