the "palazzo borgia", on the third side of the piazza, was built as the palace to house the bishops who would travel to pienza to attend the pope. inside the palace there is the diocesan museum, and the museo della cattedrale. the collection includes a lot of religious artifacts. paintings include a 7th-century painting of "christ on the cross" ("la croce"), 14th century works by pietro lorenzetti ("madonna with child") and bartolo di fredi ("madonna della misericordia"). there are also important works from the 14th and 15th centuries, including a madonna attributed to luca signorelli.