by Giuseppe Agostino Pietro Vasi, 1747

The original name of the gate was Porta Ostiensis, because it was located at the beginning of the Via Ostiense, the road that connected Rome to Ostia. The Via Ostiense was an important road artery, as evidenced by the fact that upon entering the gate of the same name, the road split, with a single direction leading to the famous Emporio, the large market of Rome.

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

The structure was built by 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 the Italian Porta San Paolo, because it was the exit from Rome that led to the Basilica of St. Paul Outside the Walls.