The so-called Piasts' Castle in Gliwice dates back to the mid-14th century. It consists of a tower from 1322, which was originally part of the city walls, and an adjoining building which was probably an armory. Modifications were carried out in the 15th century, between 1558-61 it became the residence of Friedrich von Zettritz. Later it was an armory, a jail, a magazine and since 1945 a museum. Between 1956-59 it was thoroughly rebuilt and partially reconstructed. Since that time it is claimed to be a Piast castle, although no sourced evidence backs this claim. Since 1959 the castle has been part of the Gliwice Museum.
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.