The Castello Svevo ('Swabian' or Hohenstaufen Castle) was originally built by the Saracens on the ruins of the ancient Rocca Brutia, around the year 1000. The castle was restored by Frederick II, Holy Roman Emperor, adding the octagonal tower to the original structure, in 1239. According to tradition, his son Henry lived in this castle, as a prisoner at his father's command. Louis III of Naples and Margaret of Savoy married in the castle and they both settled there in 1432.
All signs of the ancient Saracen structure have now disappeared. In the internal cloister, the modifications made by the Bourbons in order to convert it into a prison can also be seen. The entrance-hall is covered by ogival arches with engraved brackets. A wide corridor is dominated by some fleur-de-lis from the House of Anjou coat of arms. They are engraved on the ribbed Hohenstaufen arches.
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.