Originally this was the baronial palace of the Barberini constructed on a former fortress. Its present form is the renovation by Prince Camillo Pamphilj who in 1651 wished to create an ideal city, the so-called Pamphylia City that would include not only the building but also the nearby church and other buildings such as stables, warehouses, homes. The palace has 365 rooms, many of which are frescoed. During the war, the palace was home to the citizens of Valmontone. Today it is headquarters of the social life of the country and houses the Historical Museum of Valmontone.