Clemente Rospigliosi, who died in 1981, endowed the palace to the diocese with instructions to preserve it and some of the contents in part as a museum dedicated to his papal ancestor.
Among the works are an altarpiece by Fra Paolino and a Bath of Bathsheba by Sebastiano Vini.
Other painters in collection are Jacopo Vignali, Lorenzo Lippi, Felice Ficarelli, and a Death of Germanicus attributed to a follower of Nicolas Poussin.
Among the works by Giacinto Gimignani displayed are: The Diocesan Museum was moved from the Bishop's palace on via Puccini here in 1968.
In addition it has a Holy Conversation by Bernardino del Signoraccio; processional standards by Sollazzino (c. 1460–1543) and Scalabrino (1489-1561).