I highly recommend the Scavi (means excavation) Tour under St Peters Basillica. They only allow about 20 people per tour group and you have to request months in advance by going to their website and getting the fax number. Not recommended if you are very clausterphobic or are of a larger size.Some of the halls are extremely narrow. But worth the tour if into history. Unfortunately no photos are aloud once inside so this is all I got.