The Veletržní Palace is the Czech National Gallery's modern art collection, housed in a vast 1920s Functionalist trade fair building in Holešovice. The building itself is remarkable — a huge atrium flooded with natural light, with galleries arranged around the open void. It influenced Le Corbusier, who visited during construction.
The collection spans 19th- and 20th-century Czech and international art, with strong holdings in French Impressionism and Post-Impressionism. Most significantly, it houses Mucha's Slav Epic — twenty enormous paintings, each the size of a small house, depicting scenes from Slavic mythology and history. The Epic took Mucha eighteen years to complete and was his life's work. Allow half a day.