Hajnáčka castle was built in the Gothic style against the Mongol invasion in the mid-1200s. Later, in the mid-15th century, the construction was finished. Hajnáčka was the seat of important feudal lords. In 1545 the castle was besieged and conquered by Ottomans. At the end of the 16th century and the first third of the 17th century castle was an important part of the anti-Turkish defensive line. Nevertheless, it Turks in 1645 again briefly occupied for few years. In the 17th century the castle was only partially inhabitated. In 1703 it was burnt down and no longer restored.
Today the remains of walls stand on the top of the hill which is hard to reach.
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.