Tour Guide Assistance

Hey, all your Euro-readers out there -- especially the ones in Belgium (I'm looking at you, Vaara and Scott -- I need some help. I've some American expat friends visiting me in Brussels next weekend, and they are expecting a grand, memorable time. The only trouble is, I don't really have a clue what to show them. Brussels is basically my little work hideaway, so I can't admit to much substantial, interesting regional tourism. (Shameful, really, since I've been lingering around here for about three years now.) Even when I was first dating Katrien, when she was living in Leuven, we just slummed around in cafés. I know about the 'touristy' spots in Belgium -- Brugges, the bigger museums in Brussels and Antwerp, and the Ardennes, etc.; but I'm looking for something a bit off the beaten path. Any suggestions?