Corbera Castle is an impressive Muslim fortress, whose foundations lay on Roman remains. It has an irregular base, following the shape of the hill on which it rests. It was constructed in the 11th century to control the foothills of Murta and the coast. It is still possible to see the wall, the buttresses of the parade enclosure and the albarrana tower, which dates back to the Almohad period and it is one of the best-preserved towers in Europe. The complex was almost totally destroyed in 1521, during the Revolt of the Brotherhoods.
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.