The Kattlunds farm (Kattlunds Gård) was established in the Middle Ages. There are still some original buildings remaining (like stable), the newest ones were built in the 19th century. The ruins of medieval defense tower are located close to the farm. Kattlunds is owned today by Gotland Museum and is open to the public in summer season. There is also a giftshop and café.
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.