This pretty unknown building was built in 1653 and edited few times until 1726. It used to be a college for jezuit students. There was also a school for those students. Later it became multifunctional building with weather station and astronomical observatory. In 1622 a library was built in here.
Nowadays it is residence of Czech national library and Czech technical library. Since 2010 the building is being reconstructed by Prague. This is classic example of not enough known building, although it is definitely worth seeing.