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 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.