Burgruine Aggstein is the remnant of a castle on the right bank of the Danube, north of Melk. According to archaeological excavations of the foundations of the castle it has been inferred that the castle was built in the early part of the 12th century. The castle was built by Manegold III Aggsbach Getbeen of the Kuenringer family descent and his son Aggstein Manegold IV inherited it as a fiefdom of Bavaria. They started living in the castle from 1180 onwards. Its notoriety was due to the 'robber barons' of Schloss Schonbuhel and Burg Agstein' who imprisoned their rivals for ransom and tied them to a rock ledge all the time threatening to kill them by throwing them into the gorge. In 1181, it came into the possession of the Kuenringer Aggsbach-Gansbach. The castle was besieged during the revolt of the Austrian nobility against Duke Albrecht I in 1295/96. Kuenringer Leutold occupied the castle from 1348 to 1355 and then it fell into disrepair.
In 1429, Duke Albrecht V pledged to rebuild the ruined castle because of its strategical point on the Danube. The purpose was to collect taxes from passing boats. In 1438, he built a riverbank toll house to regulate shipping on the Danube and used it as a front to accumulate wealth by robbery from ships. Later, another dishonest baron, Georg von Stain, occupied the castle but in 1476 he was caught and expelled and was forced to surrender the castle. Duke Leopold III took over the castle in 1477. It was occupied with tenants and carers in order to stop the looting which had taken place on the river in previous decades.
In 1529, the castle was burned down by a group of Turks during the first Turkish siege of Vienna. It was rebuilt and provided with loopholes for defence with the help of artillery. In 1606, Anna Baroness acquired the castle, but after her death, the castle was neglected. In 1685, the castle became the property of Count Ernst Rüdiger von Starhemberg. Then in 1819, one of his descendants, Ludwig Josef Gregor von Starhemberg, sold the castle to Count Franz von Beroldingen who renovated the castle in the 19th century. The Beroldingen family owned the castle until 1930 when the estate and the ruins of Schönbühel Aggstein were sold to Count Oswald von Seilern Aspang.
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.