Only foundations and one gate-tower have survived of the so-called fortified Tafelgut that used to belong to the bishop of Tallinn.
The castle was erected on a hill by the Porkuni lake in 1479 by Simon von der Borch. Cannon towers stood in the corners of the camp castle shaped as an irregular rectangle. The circular wall and the towers did not probably reach their height all at the same time, but in the course of a longer period. This claim is backed up by the gate tower - rectangular at the bottom and octagonal at the top. The machicolation frieze adorning the top of the tower dates back to a much later time, as proved by comparing the engravings of Porkuni produced in the 17th and 19th centuries. The castle was severely damaged during the Livonian War. The castle tower currently houses museums.
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.