Bjelaj castle, locally known as Stari Grad Bjelaj (Bjelaj old town), is a medieval town-fortress complex near the village of Bjelaj, Bosanski Petrovac.
Located on the edge of the Petrovac plain (or part thereof Bjelajsko fields), on the northern slope of the Osječenica mountain. The area around the city is uninhabited and lean. The whole complex is situated on a plateau about 850 metres long.
On the south end of the northern half, there is a great fort, a prehistoric site from the Bronze and Iron Age. On the north end, there is a small fort. The fort itself has two parts: a medieval southern and northern Ottoman part. The medieval town has a ground plan of an irregular rectangle over 40 meters long and a width of about 35 meters. From the tower on the west side is the beginning of the remains of a large pen that was added along with the medieval city in the Ottoman period.
First mentioned in written sources in 1495 and named after the whiteness (or tint) by which it stood out above Bjelajsko field. Between 1530 and 1537, Bjelaj came under Ottoman rule.
Bjelaj has two parts: the southern medieval and northern Ottoman part. The medieval city has a layout of irregular rectangles over 40 m long (north-south) and about 35 m wide (east-west). The entrance to the city is in the northward.
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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.