The Valkhof is on a hill overlooking the river. It is the site of a former Charlemagne fortification and the surviving Carolingian elements are quite modest. There are two buildings with a Carolingian element. The first is an octogon chapel built in the style of Aachen in the 8th or 9th century. The initial building was constructed about 1000 and rebuilt about 1400. It used material from Charlemagne's fortification and we think we could identify some of these Caroilingian flat bricks. The second building is the ruin of Barbarossa's chapel that incorporated several Carolingian capitals on Roman pilars in the chapel.
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.