The Porta San Sebastiano, the largest and and best-preserved gate in the Aurelian Walls, was originally known as the Porta Appia, after the arterial road that it served, namely the Via Appia.
The gate was later renamed in honour of Saint Sebastian, whose relics are kept in the nearby church of San Sebastiano fuori le Mura(St Sebastian Outside the Walls) on the Via Appia.
Rebuilt in the 5th century by the emperor Honorius (r. 393-423), the Porta San Sebastiano now houses a small museum devoted to the history of the Aurelian Walls, the longest (19 km) set of city walls in the world.
On the inside of the gate there is an image of St Michael the Archangel. The accompanying inscription recalls the victory by the Romans over Robert of Anjou, King of Naples, which was secured on the saint’s feast day in 1327.