In the crypt of the previous Basilica ugoniana and in the surrounding space there are many materials that were reused. They are set in walls or exposed, examples of which are capitals, trabeations (horizontal beams), friezes and especially shafts (columns) brought from the ancient forum and from a temple dedicated to Bona Mater. Two to three metres under the churchyard there is a foundation wall 11 metres long, the execution of which can be seen in the wall above the cathedral, an opus quadratum wall of travertine. Also present are a drain spout for draining the water coming from the cistern, a closure slab, a reserve for the overflow, a round well made of stones placed in a helical formation (curve in a 3 dimensional space), and a perfectly preserved wall, in vittatum, made of ashlars of dark pink limestone.

Also present there is a sarcophagus made of Luni marble dating back to the III century; a marble box, measuring cm 203 x 65 x 57, which, according to tradition, was reused to bury Saint Rufino, martyred in 238. It is decorated both on the front side and on the short sides with a representation of the myths of Diana and Endimione. The back side is unfinished and has some remnants of a 16th century fresco, representing a prelate saint lying down. A bas relief sculpture represents a scene of innocent love between a Night Divinity and a shepherd. A reading of the characters – twirling loves, winged genii, nimphs and divinities, flocks – is quite easy, in spite of some signs of decay (the frequent use of a drill is undeniable). The entrance to the museum is from the square. On the south side of the square there is a stone wall with ancient commemorative stones, decorations, and inscriptions. On the east side is the Romanesque fa├žade of the cathedral with the bell tower. Up the hill you can clearly see the 14th century Rocca Albornoziana.