The Diocesan Museum of Fermo is located in the historic center of the city next to the Metropolitan Cathedral Basilica. The Museum was inaugurated in 2004 and was strongly desired and followed in its realization by the Archbishop Mons. Cleto Bellucci. Of great interest is the Sala del Tesoro, so called because it houses the most precious objects of the Cathedral's treasure and is the first room of the Diocesan Museum. Here we find the beautiful Missal de Firmonibus, an illuminated manuscript by Giovanni di Ugolino da Milano in 1436 commissioned by Giovanni De Firmonibus from which it takes its name. This codex, an extraordinary example of Gothic art, contains thirty-one illuminated, decorated or historiated initials, two pages with large friezes and marginal miniatures, two full-page illustrations. The best known page is certainly that of the Cavalcata, where the historical procession in honor of the Assumption is depicted. the Stauroteca, a reliquary cross donated by Francesco Todeschini Piccolomini, future Pius III, in 1503, certainly its construction is much older and of Venetian manufacture, due to the filigree decoration. In the terminations of the arms there are miniatures representing on the front the protagonists of the Crucifixion, on the reverse the symbols of the Evangelists.