Around 1076 Archbishop Gebhard of Salzburg, a follower of Pope Gregory VII in the Investiture Controversy, had the Petersberg fortress erected above the town in order to prevent Emperor Henry IV from crossing the Alps. The archbishop also had fierce enemies in the Carinthian ducal House of Sponheim, who after his deposition made several attempts to take possession of Friesach. Constant attacks by Duke Engelbert were finally repelled in 1124. In 1149 King Conrad III of Germany stayed at the castle on his way back from the Second Crusade, as did Richard the Lionheart returning from the Third Crusade in 1192, attempting to elude the guards of Duke Leopold V of Austria.
Today the castle is home to the Friesach City Museum, which features exhibits about the town's history, culture, mining industry and trade.
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.