Whatever else might be said about it all, the architecture of St. Peter's is amazing. Though I'm not aware that Peter ever got anywhere near there, you can hear echoes of the disciples as they came out of the Jerusalem temple, "Master, see what manner of stones and what buildings are here!" (Mark 13:1).
Imagine their disbelief at His response, "there shall not be left one stone upon another, that shall not be thrown down." Followed by the warnings of great and terrible things yet to come.
The concluding thought, for then and now, "watch and pray."