In the 13th century, it was replaced by a new church with an underground chapel dedicated to St. Eleutherius. After the latter had been destroyed by an earthquake, the actual Cathedral of Saint Clement was built between 1659 and 1662.
On the facade, we can see a Renaissance portal of 1512, work of Trojano di Palestrina.
The inside of the church is laid out with three naves; the main altar shows a ciborium overcome by a Cosmatesque style aedicule. The apse is decorated with 14th century frescoes, recently restored. You can observe the 16th century gilded wooden organ with angels and the 14th century icon of Our Lady of Graces. The portal leading to the sacristy was built in 1483 and alongside is a 15th century fresco of the Madonna and four Saints.
In the Crypt where you can see parts of medieval frescoes, are the relics of the martyrs St. Eleutherius and St. Pontianus.
The Diocesano Museum is found in the cloisters of the Cathedral.