Here’s how you can see St Peter’s in Rome without the crowds. It’s the church of San Pietro in Vincoli (St Peter in Chains). It isn’t as large or impressive as St Peter’s Basilica, and not as well known, but it does have some interesting things to look at inside.
The statue of Moses on the tomb of Pope Julius II is by Michelangelo. And beneath the main altar you can see the actual chains that bound St Peter when he was imprisoned in Jerusalem … maybe. The church is not far from the Colosseum, but can be a bit hard to find.