Autoworld Brussels
The last museum I visited while in Europe was Autoworld Brussels. It is a large museum right in the middle of Brussels and has a large collection of interesting cars, including former royal cars of the Belgian royal family.
It was a very nice museum, although not as good as the Louwman Museum. If you’re in Brussels it is worth a visit. For a European museum there is a surprising number of American cars there. There are also some nice pre-war cars.