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 Clementinum is a historic complex of buildings in Prague. Until recently the complex hosted the National, University and Technical libraries, the City Library also being located nearby on Mariánské Náměstí. The Technical library and the Municipal library have moved to the Prague National Technical Library at Technická 6 since 2009. It is currently in use as the National Library of the Czech Republic.
Its history dates from the existence of a chapel dedicated to Saint Clement in the 11th century. A Dominican monastery was founded in the medieval period, which was transformed in 1556 to a Jesuit college. In 1622 the Jesuits transferred the library of Charles University to the Klementinum, and the college was merged with the University in 1654. The Jesuits remained until 1773, when the Klementinum was established as an observatory, library, and university by the Empress Maria Theresa of Austria.