Prague is most famous for its Gothic, Renaissance and Baroque architecture, but the Art Nouveau style (known as Secese in Czech and Jugendstil in German), which you should look out for while sightseeing, also helps give the city centre its special character.
Art Nouveau developed in the late 19th early/20th century and became very popular throughout Europe and beyond. The movement was inspired by natural forms, resulting in elegant flowing lines and an abundance of curves, in architecture, art and furniture design. Famous exponents of the style include Victor Horta in Brussels, Gustav Klimt and Otto Wagner in Vienna and Charles Rennie Mackintosh in Glasgow. Each of them interpreted the style in slightly different ways, and distinctive local branches of Art Nouveau emerged.
In the Czech lands Art Nouveau was associated most of all with the artist Alfons Mucha (see Bohemia Apartments blog article on Alfons Mucha), whose poster designs are synonymous with the style. Art Nouveau architecture was equally important, and architects such as Osvald Polívka, Antonín Balšánek and Josef Fanta enthusisatically embraced the style.