Saint Sebastian Gate (Porta San Sebastiano also called Porta Appia); south part of the Aurelian Walls. It is the largest and one of the best-preserved gates passing through the Aurelian Walls. The gate sat astride the Appian Way (Via Appia)- The Aurelian Walls (Mura aureliane; mur d'Aurelien; Die Aurelianische Mauer ) are a line of city walls built between 271 AD and 275 AD in Rome during the reign of the Roman Emperor Aurelian.(Empereur Romain Aurelien)The full circuit ran for 19 km surrounding an area of 13.7 km2.Rome; Italy. 2020.