University of Warsaw Library (Biblioteka Uniwersytetu Warszawskiego). The BUW building was opened in December of 1999. This ultra-modern library consists of two buildings: the front lobby area (the so-called Rogal) and the main section. The biggest attraction is the BUW's roof garden, which spreads over an area of more than 1 hectare, making it one of the largest and most beautiful roof gardens in Europe.