The evocative basement of the palace contains the remains of a Romanesque cloister and the crypt of the "Ugonian Basilica" (11th cent.), decorated with very rare coeval frescoes and a Roman sarcophagus with the myth of Selene and Endymion that housed the coffin of the patron saint Rufinus. The museum preserves interesting and valuable artwork from the cathedral, enhancing its historical and religious significance. Completing the site visit are the Cloister and Crypt of St. Rufinus, both from the 11th century. The crypt, an evocative environment located under the nave of the cathedral, is one of the places where Francis used to retire in prayer when he preached in the cathedral.