The evidence that Peter taught and died in Rome comes from those early writers, some by allusion and some in so many words, and from the grave itself. Irenaeus, writing in the late second century, says the Apostles Peter and Paul founded the Church at Rome and entrusted its episcopate to Linus. Benedict XVI noted that Peter ministered first in Jerusalem and then in Antioch before Rome.

For a pilgrim the question has an address. The grave venerated as Peter's lies beneath the high altar of St. Peter's Basilica, in an ancient cemetery excavated in the 1940s. In 1950 Pius XII announced that the tomb of the Apostle had been found, and in 1968 Paul VI said he judged the identification of the relics convincing, while research and debate continue. You can pray above the tomb in the basilica; the excavations beneath it are shown only on guided visits arranged in advance with the basilica.

Christians of other traditions read the same evidence differently, especially on what Peter's presence in Rome means for the papacy. Going there lets you weigh it in the place itself.