The piazza contains what is supposed to be the perfect Renaissance cathedral, decorated with the pope's family's coat of arms, plus a palace for the pope next door for his visits to his pet project. It may be very nice artistically but it wasn't designed well. It's built on an eroding cliff so there are cracks all over the walls that have to constantly be patched up, and there's a strong sulfur stench that comes up from the ground occassionally. The palace was closed the day we were visiting, so we had a shorter than usual visit.