Probably built in 837 by Orso I, the Monte Sant'Angelo Castle has bastions of different ages. The most ancient part, called Torre dei Giganti ('Giants' Tower') is a pentagonal tower 18 m-high, with walls 3.7 m thick. The first documents on its history dates back to 979; later, it was the residence of Rainulf I of Aversa and the Robert Guiscard, who built the Norman Tower and the Treasure Hall.
Emperor Frederick II restored the construction to use it as residence for his mistress Bianca Lancia, while under the Angevines it was used mainly as prison. Later, from 1464 to 1485, the fortress was the residence of the exiled Albanian condottiero Skanderbeg. The castle was largely rebuilt in the late 15th century by Ferdinand I. According to a legend, the castle is currently home to the ghost of Bianca Lancia, whose sighs can be heard especially in the winter time. Today the castle is used for exhibitions.
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.