Casimir III the Great erected a castle in Ko³o – most likely prior to the founding of the city – as part of an overall enterprise of strengthening the boundaries of the realm. Ko³o castle was mainly intended to protect central Wielkopolska from attacks by the Teutonic Knights. The fortified city played a vital strategic role for some 200 years.
It was established as a 55 m x 40 m rectangle, made of brick with stone foundations, with its longer side arranged on a north-east, south-west axis and enclosed by high crenellated walls.
The castle slowly fell into decay from around the mid-16th century. This was mainly brought about by changes to the defence system after the invention of firearms and artillery.
The entire length of south-west line of walls to a height of 4 m (supported by abutments), fragments of the walls of the short sides of the foundation, and the tower are all that remain of the onetime castle. The north-west section of walls, on the Warta side, have collapsed due to the foundations having been eroded by the flooding of the river.
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.