The Porta San Sebastiano is the largest and one of the best-preserved gates passing through the Aurelian Walls in Rome. Originally known as the Porta Appia, the gate sat astride the Appian Way, the regina viarum, which originated at the Porta Capena in the Servian Wall. During the Middle Ages probably it was also called Accia (or Dazza or Datia), a name whose etymology is quite uncertain, but arguably associated with the river Almone, called "acqua Accia", that flowed nearby. Also called Porta Domine quo vadis because of the Church nearby. The modern usage of the phrase "Quo Vadis" refers to a Christian tradition regarding Saint Peter taht was fleeing from likely crucifixion in Rome at the hands of the government, and along the road outside the city he met the risen Jesus. In the Latin translation, Peter asks Jesus "Quo vadis?", to which he replies, "Romam eo iterum crucifigi" that is "I am going to Rome to be crucified again". Peter thereby gains the courage to continue his ministry and returns to the city, to eventually be martyred by being crucified upside-down. The Church of Domine Quo Vadis in Rome is built where, according to legend, the meeting between Peter and Jesus took place.
The present name is attested only since the second half of 15th century, due to the vicinity to the Basilica of San Sebastiano and its catacombs.