Moeche Castle was built in the 14th century by the Andrades Family. It has an octogonal groundplan, and its walls are 10 m high and 3 m thick. Its gatekeep is 18 m tall and it is the only part of the castle protecting its walls from the outside. It was under siege and taken by the Irmandinos uprising.
The Moeche Castle has been restored recently, but in order to visit the interior of the castle, you'll have to request the keys from the local town hall.
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.