15th century castle in Sarmiento belonged to the important Sarmiento family. Its last owner was the House of Alba. Acquired by the Provincial Council of Palencia, we can visit the tower, its rooms and its ramparts. It hosts an exhibition entitled PlastiHistoria, showing various scenes made in clay on the history of Palencia. Its keep has a height of 22 meters and the thickness of its walls is the largest of the Spanish castles, reaching 11 meters thick in some places
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.