The front was facing the Via Appia, decorated with statues and architectural ornaments of which some fragments are still visible today. It was built on a square base from peperino blocks; 14 m high. and 36 m wide, it consists of three archways protected on the sides by two forepart or rectangular towers, and some studies suppose that it was articulated on two floors, with access to the upper floor by means of stairways made of wood, a material probably used for the same doors.
The central fornix, the widest, was intended for the passage of carriages, cavalry and soldiers in battle gear, while the two lateral arches were reserved for the passage of pedestrians. The main left door (like the rest of the walls) also had a square structure; it consisted of three arches, of which the central and right lateral ones and a posterula, still visible today, are still preserved.