For only a few euros you can get a guided tour in this monumental gothic building. Definitely worth the visit.

Town Hall (Stadhuis), Great Market Square 9, Leuven, Belgium
http://www.visitleuven.be/nl/town-hall
+32 16 20 30 20

Visited May 2013. You can find my review about Town Hall (Stadhuis) also on TripAdvisor.