The Porta Asinaria is a gate in the Aurelian Walls of Rome. Dominated by two protruding tower blocks and associated guard rooms, it was built between 270 and 273, at the same time as the Wall itself. It is through this gate that East Roman troops under General Belisarius entered the city in 536, reclaiming the city for the Byzantine Empire from the Ostrogoths.
By the 16th century it had become overwhelmed by traffic. A new breach in the walls was made nearby to create the Porta San Giovanni. At this point, the Porta Asinaria was closed to traffic.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.