At the end of the 14th century, Teutonic Knights built a castle in Ryn, serving as a base for fighting with the Lithuanians. Until 1525, the castle was the seat of the commander. After two years of the construction of the castle, then the Grand Master of the Order Winrich von Kniprode arrived in Ryn to inspect and take over the castle, and returned to the Malbork by waterway. In 1723 Ryn received city rights granted by the Prussian King Frederick William I and in 1853 the castle was converted into a prison. Since July 2006, the castle operates as a hotel.
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.