As a great fan of Otto Wagner i have visited this museum already twice. Be ready to immerse in Art Nouveau (Jugendstil or Secession or Modern or Liberty or Tiffany are the same names) style. Fantastic stained glass, golden floral decoration, roman-style bath and swimming pool, all this will make you fall in love in one of the Wagners masterpieces. Visit it 100% if you have more than 1 day in Vienna because its located far away from the city center.