In 1325, the Teutonic Knights built a castle called 'Yladia' or 'Ilaw', later known as 'Preussisch Eylau', in the center of the Old Prussian region Natangia. Ylow is the Old Prussian term for mud or swamp. The settlement nearby developed slowly, but in 1348 the Teutonic Order gave the privilege to establish twelve pubs at the surrounding area of the castle. Even though the village had only a few inhabitants, due to its central position it was often used as meeting place for different officials of the Order. In 1427 e.g. the Eylau County Law (Eylauer Landesordnung) was published by the Order.
Throughout the Thirteen Years' War the castle was besieged on May 24, 1455 by troops of the Prussian Confederation under the command of Remschel von Krixen, but the garrison defeated these troops. Also throughout the Horsemen's War in 1520 the castle was unsuccessfully besieged by troops of the Polish Kingdom, which caused a devastation of the village itself.
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.