Oponice Castle was probably built in the second half of the 13th century by son Peter from the Csák clan. The castle was first mentioned in 1300 as 'Oponh'. Until the death of Máte Csák of Trencsén in 1321, Oponice Castle guarded part of his wide domain in the central Nitra area. The castle was later administered by the royal exchequer until it was passed in 1392 into the hereditary possession of Nicholas Ewres, founder of the Apponyi dynasty.
The castle was expanded and its defenses strengthened, particularly during the threat from Ottoman Turkey, allowing it to withstand enemy onslaughts. Unfortunately, a family dispute over land dating from 1612 meant the end of the castle, punctuated by a fire in 1645 which caused the castle owners to finally abandon it. From time to time the castle was used by the Kurucs, Hungarian insurgents fighting the Habsburgs, until Imperial forces conquered it and had the castle demolished in the early 17th century. The castle's aristocratic tradition remained bound to the Apponyis, who maintained and preserved it until the death of the final descendant from this family, Henrich Apponyi, in 1935.
The castle’s distinct silhouette covers the preserved gun bastion and northeast Renaissance castle up to the third floor.
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.