The 'Ravelijn op den Zoom' (ravelin) is the last remnant of the fortifications designed by Menno van Coehoorn. The ravelin consists of a island with earthen and stone walls, surrounded by a wide moat. The ravelin is one of the few remaining parts of the extensive fortification system around the city. The fortress was so ingeniously designed that it was assumed that it could not be taken and therefore got the nickname 'La Pucelle' (Virgin). In 1747 the city nevertheless became occupied by French troops.
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.