Ojców Castle was part of a system of castles known as the Eagle's Nests - formerly protecting the southern border of the Kingdom of Poland. Currently it houses a museum dedicated to the castle in its renovated castle-tower. The castle was used as a stronghold, built by Casimir III the Great in the second half of the 14th century.
A legend mentions, that the caste was built by the Duke of Wrocław Wiesław I, Popiel's brother-in-law, however te first recorded information about the castle comes from the fourteenth century - linking up with King Casimir III the Great, who used the castle as part of his defensive line against the Kingdom of Bohemia and the south. The King was called the castle in honour of his father, Władysław I Łokietek, calling it Father by the Rock. In 1665 the stronghold was taken over by the Swedes, which they partially burned and deconstructed. The House of Koryciński, who owned the castle, had renovated it, and built additional living quarters. Various battles throughout the oncoming centuries had caused the castle to be shifted between different owners. Causing the castle to go through several cycles of renovation and deconstruction, currently the castle stands as the picturesque, and renovated ruin.
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.