Château de Kaysersberg was built for Albin Woelflin, imperial bailiff for Frederick II, Holy Roman Emperor, around 1220. The site was acquired in 1227 by the lords of Horbourg and Ribeaupierre. It had an important strategic role as it allowed the Empire to close off one of the routes across the Vosges Mountains towards Lorraine.
The circular keep is the oldest part of the castle and one of the first of this type in the upper Rhine valley. It was designed at the same time as the keep at the Château de Pflixbourg. The first curtain wall, which included the keep, was replaced after 1261 by a wall enclosing the keep, according to a contemporary plan, which allowed an uninterrupted circuit of the walls and strengthened defences on the side likely to be attacked. In the 14th century, the castle was the residence of the imperial provost or bailiff. Following a fire, the enceinte was raised to 4 m.
In the second half of the 15th century, the castle defences were modernised in response to developments in artillery and firearms; the crenels were closed with wooden shutters, the merlons were equipped with firing slits and the round walk was completely covered. In this period, the castle was merely a sub-bailliage and personnel were heavily reduced. During the German Peasants' War (1524-1525), the castle was besieged. It was restored by Lazarre de Schwendi in 1583.
According to archaeological excavations and studies, the castle was abandoned at the end of the 16th century. After the French Revolution, it was declared a national asset and sold to François Joseph Boecklin de Boecklinsau, who planted vines, and later passed to the Bastard family.
The castle is largely built from granite. It stands at an altitude of 295 m and dominates from 50m the north side of the town. The castle has a triangular plan dominated by the circular keep in the highest point. The keep is 11 m in diameter with walls 4.42 m thick. The original parapet has been kept to a height of 0.55 m, with the crenels and merlons restored. The spiral staircase is concrete. Access is to the first floor, through an arched doorway.
The spacious third floor served as a storeroom and provided access to the platform which was originally covered. The keep had a purely military function. The main residential buildings were situated against the east curtain wall. On the other side, towards the town, was a large lower courtyard. The entrance to the castle, in the east, was by an arched doorway with a barbican; to the left is a cruciform cannon opening and a circular firing hole. The castle's enceinte is linked to the town's by curtain walls with a round walk.
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.