Sommerau Castle was built on a rock spur around which the Ruwer river flowed on three sides. In the 13th century the castle was built by the Trier knight family 'von der Brücke', who had their ancestral seat in the Barbarathermen. The castle had fallen into disrepair by the beginning of the 19th century at the latest.
The facility measures 40 x 10 m. In the west, the remains of the former palace or residential building tower up to a height of 10 m, and in the east, the four-storey square keep, which with its four floors also served as a residential tower, is around 16 m high. Apparently an ascending wooden battlement led to a door about 3 m high. To the south on the fourth floor there is a large rectangular door with a toilet bay, the masonry of which is placed on consoles made of red sandstone. The residential building shows, recognizable from the inside, three full floors and half a fourth with the protruding remainder of a chimney that begins on the second floor. Only remnants of the rising masonry can be seen of the surrounding wall that supported the battlements. The remaining transverse walls are in the ground, the ground plan can only be determined through excavations.
Today the ruins are freely accessible.
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.