Walibi Belgium is one of the country's main amusement parks, close enough to Louvain-la-Neuve to work as an easy day out. The big draw is the roller coaster lineup, including Kondaa, Vampire, and the wooden Werewolf, but there are gentler rides too.
It is a full-day place rather than a quick stop. Check the seasonal calendar before going, especially outside summer and school holidays.