The one-time home of the eponymous first director (1828–1905) of the Museum of Applied Arts has recently opened and is a shrine to art nouveau/Secessionist art, showing items from the museum (now under renovation). Rooms on the first floor include Ráth's fully furnished study and dining and sitting rooms; other galleries on the same floor and the one above walk you through the history of the style in France, Austria and Britain as well as Hungary. An absolute gem.
György Ráth Museum
Top choice in Budapest