Here is another World Heritage Site in Brussels that has been listed but is difficult for the public to access. Three of the four houses are really difficult, although there are some limited opening times for one of them..

Unlike the other three Victor Horta houses in Brussels that are part of the World Heritage Site, the Horta Museum does give you the opportunity to go inside one of the original buildings and get a sense of the design and layout.

Rather than just read about the influence on Art Nouveau architecture, you can see it for yourself. Rather than just look at each element in books or online, you can feel how they merge together. The opening hours are still somewhat limited, though.