by Giuseppe Agostino Pietro Vasi, 1747

The gate's original name was Porta Ostiensis, because it stood at the start of the Via Ostiense, the road linking Rome to Ostia. The Via Ostiense was an important thoroughfare, as shown by the fact that on entering the gate of the same name the road divided, with one branch leading to the famous Emporium, the great market of Rome.

The gatehouse is flanked by two cylindrical towers and has two entrances, which had been covered by a second gate with a single opening, built in front of the first by the Byzantine general Belisarius (530-540).

The structure is owed to Maxentius, in the 4th century, but the two towers were raised by Honorius. Its original Latin name was Porta Ostiensis, as it opened onto the road to Ostia. It was later renamed Porta San Paolo in Italian, because it was the exit from Rome leading to the Basilica of San Paolo fuori le Mura.