One of the buildings in the Parc du Cinquantenaire is a museum called Autoworld. Unlike the military museum next to it, it's not free. And personally, I didn't find the price to really be worth it. The most interesting thing about it is the number of European automobiles, but even that selection isn't as large as you'd think. If you go to Brussels, my advice would be to either check out the military museum or just stroll around the park. It's a large and rather pretty park.
