It now houses a modern art museum, Museo Emilio Greco, highlighting the sculptor's works.
Construction palace was begun in 1297 by Pope Boniface VIII, but work continued for decades.
In preparation for a visit in 1493 to Orvieto by Pope Alexander VI, the external staircase leading to a loggia was built.
However in 1504 a crowd gathered on the roof of the palace to watch the local horse race, caused a collapse.
Presently the palace sports a merlionated roofline and a piano nobile with large mullioned windows.