In a manner of speaking this is a museum and this isn't a museum. The Horta Museum isn't what you would normally think of as being a museum – as in there are objects in the museum to look at. Instead, the BUILDING itself IS the museum. The Horta Museum is the house that Victor Horta built for himself in the late 1890's. And it's considered to be a terrific example of the architectural style that made him one of the most acclaimed architects in Belgium. The Art Nouveau style was extremely popular in Brussels between 1893 and 1918.
When you go see the Horta Museum you will notice the use of industrial materials like steel and iron in the visible parts of houses. There will also be decorations inspired by nature (e.g. the famous whiplash motive especially in the work of Horta), and decorative mosaics on the house façade. Interesting note: the Horta Museum demonstrates the most innovative approach even seen in architecture - all the rooms being built around a central hall. To achieve that he used a glass ceiling that allows light to fall into the house in a natural illumination