The Angevine-Aragonese castle of Gallipoli dates back to the 13th-14th centuries, but the town used to have a stronghold already during Roman time, together with towers enlarged by the Byzantines and by the Normans. The Angevins and the Aragonese modified the structure of the fortress, but Francesco di Giorgio Martini was the one who made important changes. During the 19th century the moat was filled up and the arches which used to support the lift bridge were filled in.
The fortress has a square base strengthened by the four towers. The tower Vedetta, topped by merlons, has a polygonal shape. The other towers are surrounded by a string course and are decorated with small arches. The eastern curtain, the Rivellino, is a fifth circular tower separated from the rest of the walls and has not been renovated yet. Inside it, there are large rooms with barrel and cross vaults.
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.