Peter's presence in Rome is indicated in his first letter. The
name "Babylon" is used here as a cryptic name for the
city of Rome, a characteristic of writings done during times of
persecution. During Peter's time (witnessed by his own
martyrdom) and most New Testament times (witness the
Book of Revelation--classic persecution literature), Rome
took on the characteristics of the most outstanding example
of a world power hostile to God--ancient Babylon.
1 Peter 5:12-13
I write you this briefly through Silvanus ... The
chosen one at Babylon sends you greeting, as
does Mark, my son.