Hellenburg Castle was probably built around 1300. After some renovations and additions, which took place in the 14th and 15th century, the castle got its final shape in 1450. The castle was lost as a result of a flooding caused by a storm disaster in 1477. In the 17th century nothing more remained than a ruin. These ruins were demolished in the 18th century, its stones used as building materials by the villagers of Baarland and the location of the castle was forgotten. The ruins were found accidentally in 1957. Today the foundations have been reserved.
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.