Taking Rome's "B" trainline along its southern route will lead one to a stop labeled Basilica San Paulo. Unsurprisingly, this is best train stop to get off of for pilgrims headed to Saint Paul's Basilica. One of the four major basilica's of Rome, alongside to Saint John Lateran, Saint Peter's, and Saint Mary Major, Saint Paul's Outside the Walls is one of the most beautiful yet most secluded of the four churches.
A short walk from the train station will lead you to the enormous structure. You will find that the entrance a visitor is expected to use will be on the far end off the road from the train station, on the West side of the building. Luckily, this entrance is also ideal as it leads through a beautiful courtyard surrounded by Corinthian columns and an enormous statue of Saint Paul in the center. Entering into the Basilica proper, one can see perhaps the most famous part of the great structure — the papal artwork. Circling throughout Saint Paul's is artwork depicting every pope who has ever lived — including the most recent. Every time a new Pope is chosen one of the empty spaces is filled in and their likeness added to the Basilica.
Another prominent element of this Basilica is that (like St. Peter's Basilica) Saint Paul is buried beneath it. If one is looking for a place to attend mass while in Rome, next to the bones of such a great saint is well recommended.