The Diocesan Museum of Velletri is located seventeenth century in the former workshop of the complex attached to the San Clemente cathedral. The museum's collection includes works of art from the churches in the city. The most valuable work in the museum is the Crux Veliterna, a reliquary in filigreed gold, precious stones and enamel, made by goldsmith Palermo dating from the eleventh or twelfth century. Containing traditionally a fragment of the Cross of Christ, was donated by Frederick II of Swabia in Rinaldo of the lords of Ienne, then Bishop of Velletri and later elected pope under the name of Alexander IV, who in turn donated it to the cathedral Velletri. Among the other works of art in the museum, a Madonna and Child with Two Angels by Gentile da Fabriano, the only work of his stay in Rome between 1426 and 1427. In addition, there is a Madonna of the Rosary work of the Neapolitan School painter Sebastiano Conca . At the headquarters of the museum is also active, an exhibition hall that houses temporary exhibitions.