The Barbican, the 15th century bastion with a circular floor plan used to belong to the wall system of the Bishop's Castle. Its construction is linked to the visit of General Pál Kinizsi, who came to the town in 1498. In the shadow of the Turkish threat the defence systems of castles and towns were strengthened all around the South. The Gothic-style gate tower was built in the 15th century at the western corner of the high castle wall. The Barbican is a round gate tower sitting on a narrow column. Its back gate served a specific purpose: it enabled the defenders to attack the attacking enemy getting in the gate from the side. The Barbican is surrounded with the remains of the castle ditch and you can walk up to the entrance on the old drawbridge. The pulleys of the drawbridge are still displayed inside.
There is a fantastic view opening towards the town from the top of the bastion. You can walk along the machicolation (the wooden walkway) on the top of the Barbican.
After defence structures became obsolete during the 18th-19th century, similarly to other parts of the town, houses were built around the castle wall. The buildings that were built along the castle walls were demolished in the 1960s making the old Barbican as well as other parts of the wall free and visible again.
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.