Sorry, Tex; there aren't any plazas in Rome.
I meant St. Peter's square. I had heard that the ceremony would be held in the square.
Golly, professor. Lookie at what I found:
The popular Campo dei Fiori market in the historic center, occupying an entire piazza, has been an institution since 1477, when it was moved from the Piazza Navona. Cardinals and noblemen mingled with fishmongers and foreigners, making it one of the liveliest areas of medieval and renaissance Rome. Lively, indeed: Many of the piazza's inns were once owned by the 15th century courtesan Vanozza Catanei, who was mistress of Pope Alexander VI Borgia.
As you know, professor, "piazza" is Italian for "plaza."
There are many other piazzas in Rome. I can list them if you'd like.