Castle of the Masovian Dukes in Ciechanów was built on the turning point of the fourteenth and fifteenth century by Prince Janusz I (1379-1429). The towers located in the four corners of the castle's square formation help to defend the stronghold, and additional 10 metre high defensive walls. Due to dozens of reconstructions and expansions of the castle, the militaristic stronghold transformed into a royal residence. In the fifteenth century, the castle was raised by an additional level and a raised courtyard.
In 1547, the stronghold changed its function into a aristocratic residence. It was the last period of the stronghold's glory. After the Third Partition of Poland, the stronghold became part of Prussia, and was partially deconstructed for cheap building material. In 1818, the castle was owned by the House of Krasiński, in the twentieth century the castle was fully rebuilt.
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.