Rome - St. Paul's Outside the Walls(Basilica San Paolo Fuori le Mura)

That church is in south Rome (not within the Vatican). I think it is south of what is shown on most Rome city maps. Going south and a little east from the colosseum, there is the Baths of Caracalla, St. Pauls Outside the Walls and the Catacombs sort of all in a line. Try looking on a "greater Rome" map.

Mary, I looked this up in my Eyewitness Rome guide. It is listed in the "Farther Afield" section, meaning that it's on the outskirts of the city (to the south, along the river, maybe about 3 miles or so from the Vatican). The closest Metro stop is San Paolo. The little map in the Eyewitness Guide is not very detailed. I tried to find it on my Rome map, but it was too far south to be listed. I hope you are able to find this!