The National Gallery offers several free admission days a year and one is coming up in March.  On this date you will be able to visit the exhibitions of artists Stanislav Kolíbal and Kurt Gebauer, and also the exhibit of the architectural style of structures built during the 1960s through 1980s in Czechoslovakia called Brutalismus.  The exhibits are at the Veletržní palác (Trade Fair Palace) in Prague 7.