…kind of an architectural/archeological question. Are there any catacombs, tunnels, or basement rooms beneath it, or is it just solid ground? And how much weight can it bear, ballpark?
I ask because of simple curiosity, and because I’m not in any way planning a trip with a giant robot. No sirree.
So, can anyone enlighten me?
I don’t know precisely what was under the piazza, but before St. Peter’s, Vatican Hill was the site of both a circus and a cemetery (in Christian legend it was the cemetery where Peter was buried, which was why the basilica was built there). There are still catacombs under the basilica, and there may be under the piazza too.
Before Roman times, the Vatican Hill probably had Etruscans living on it, but I don’t know what kind of archaeology has been done there. Probably none under the piazza.
I think the same digs that uncovered the Vatican Necropolis also did some uncovering of the circus. in the piazza.
You can take a tour of the excavation, including what is believed to be Peter’s tomb:
That’s under the Basilica. The OP is asking about St. Peter’s Square.
What, in the Roman sense was a ‘circus?’ A place of entertainment that would leave behind some sort of auditorium?
An arena for chariot races, basically. Kind of the ancient Roman version of a speedway. They staged other equestrian events in them too, but chariot races were the main event. The word “circus” means “circle” in Latin. The circus was the ring for the races. The word eventually became used for circular arenas in general.
One tunnel which will almost run under St Peter’s Square is the new Metro line currently under construction. But the fact that it will just miss the eastern edge of the Square doubtless has more to do with the need to avoid Vatican sovereign territory.
As for how much weight the ground could bear, when Domenico Fontana moved the Vatican obelisk in 1586 - that obelisk being the most visible remnant of the Roman circus - he placed it very slightly off line of the central axis of the Basilica. (Carlo Maderno’s facade of the Basilica, which is later, was built slightly askew to disguise this.) There has been some speculation that Fontana was forced to avoid his preferred site because of problems with the stability of the ground.
The excavations beneath the Basilica in the 1940s never extended eastwards into the Square simply because they came up against the foundations of the eastern end of the Basilica, much of them actually the foundations of the Constantinian Basilica. Those completely sliced through the level of the necropolis.
Underneath St. Peter’s Square? St. Peter’s Cube, n’est-ce pas?