Schengen Castle dates from 1390 but it was was torn down by the industrialist Jean-Nicolas Collart in 1812. He built a residential manor house in its place and now Schengen Castle is a hotel and conference centre.
All that remained of the medieval building was its round central tower. The castle's most famous visitor was certainly Victor Hugo who visited the Collarts in 1871 and made a sketch of the old tower.
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.