This gate, originally called the Appian Gate because of its position on the road of the same name, is the largest in the Aurelian walls and is still in an excellent state of conservation. It originally had two twin-arched gateways flanked by two semi-circular towers. 

These were later enlarged and raised another storey, and a fortified courtyard was created inside the gateway. The two arched entrances were reduced to just one, probably under emperor Honorius (395-423 AD), as seen today, and the towers were encased in two large square bases covered with marble. 

On your way out, the right gate jamb contains the figure of the archangel Gabriel engraved in the marble and also a Medieval inscription, which commemorates the victory of the city’s populace against Robert of Anjou in a battle that took place near this gate in 1327. 

The internal structures underwent many changes, above all, in 1942-43, when the building became the residence of Fascist Party Secretary Ettore Muti. Today, it houses the Museum of the Walls.