The original Saint Peter's Basilica, built in 326, as opposed to the epic basilica that exists today, was constructed in the form of a Latin cross. An atrium, called the Garden of Paradise, stood at the entrance, beckoning followers through the main doorways of the church.
Unlike pagan temples, which were lavishly decorated, the facade of Saint Peter's was plain. Thankfully, Catholicism got over all that when they made the new Saint Peter's. Of course, the downside was that the religion became incredibly corrupt, but, hey, beauty has to come at a price.
The Basilica was built on top of the old Circus of Nero, but before you start pulling out your popcorn and cotton candy, this wasn't a modern circus. The Roman crucifixions of Christians was the main act. Saint Peter, among many others, was hung up to die there. The Basilica was built on top of this anti-Christian site, as almost an intentional modification of history by Emperor Constantine, because if it no longer exists, it never happened, right?