The Lapidary Museum was founded in 1912, in the basement of the palace. New initiative that started from the idea of Bishop Grau to found a Diocesan Museum. Within a perfect framework, because the architecture of the basement reminds the models of Roman architecture, with the use of stone and brick, in a very elementary way. Of all the pieces that can be admired in this room, the Roman miliary stands out, granite landmark that was placed on the edge of the road to mark the distances on the roads.

It is also appropriate to stop before the Estela dedicated to the Capitoline Triad and the medieval tombs.