Alfons Mucha (1860–1939), the most globally-known modern artist originating from the Czech lands, gained international renown in Paris at the turn of the 19th and 20th centuries thanks to his original art-nouveau decorative works. He, however, viewed the real sense of his life in another work which was much more significant to him: in a series of twenty large-dimensional paintings, The Slav Epic, on which he worked between 1912 and 1926.
You can visit the exhibition at the National Gallery till the end of 2016. Tue-Sun 10 a.m.–6 p.m. It is definitely worth visiting.