"Roma S. Pietro train station isn't in the Vatican" Vatican City Transportation Tip by mccalpin
Vatican City Transportation: 39 reviews and 35 photos
There is a train station called Roma San Pietro. This is a train station for regional trains, on the line that runs from Roma Termini up the west coast of Italy to Civitavecchia. So, only regional trains stop here (i.e., not "premium" trains, like the InterCity or Freccia-whatever).
This train station is open to the public because it is about 400 meters south of the walls of Vatican City. It serves all the residential areas on the south side of the Vatican.
From this station two train lines lead to the "north". One runs out of town on the way to Civitavecchia, the other is the short spur that runs over the Vatican city walls and terminates in a giant metal gate. This spur leads to the train station that is inside Vatican City, which is not accessible to the public. Indeed, there is no scheduled service to this latter station, it being used only for the transportation of supplies into the City, and the very occasional important passenger.
When you use www.trenitalia.com for schedules, be sure to enter "Roma San Pietro" to get this exact station. This is the train station you would use closest to the Vatican if you were coming in from out of town - St. Peter's is about a 10-12 minute walk from here.
Look at my other transportation tip for a photo of the station inside the Vatican.