Arreskov was owned by the Crown and in 1241 Duke Abel inherited the castle from his father, King Valdemar Sejr. Some years later, the castle was captured and destroyed by his brother Erik Plovpenning. Arreskov was captured once again and destroyed in 1264 by King Erik Glipping. The present castle is third on the site, built in 1558. The castle mound is about 100 m x 35 m. The rectangular castle embankment is protected by a moat and circular outer ramparts. Today, the ramparts are partly destroyed and the castle embankment is overgrown. Not far from Gammel Arreskov stands another castle mound called Perdeholm. The castle and park is open by appointment.
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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.