The original church of Saint Peter was of medieval origin and connected to the castle. The new Church of St. Peter the Apostle, under architect Gerolamo Theodoli, was started in 1745 and finished in 1755. It is still connected to the palace by a gallery frescoed by Salvatore Monosilio.
The Church has the plan of a cross, a double entrance and side chapels.
The facade has a particular style with a spectacular Baroque effect and two bell towers in the entrance of St. Peter’s piazza.
Inside are paintings of the Zuccari school and a fifteenth-century icon preserved in the baptistery.