Are you taking children? We just spent a 48hrs there with ours (5 & 7yrs) a few weeks ago. The EU Parliament visitors centre is really fab... free to get in, really interesting and lots of interactive things for the children.
http://www.europarl.europa.eu/visiting/ ... arium.html
We had a wonderful meal at
http://www.ogenblik.be V relaxed and beautiful fish (and the meat looked v good too, but we are veggie).
We wandered all over town popping in and out of churches, looking at the buildings, eating waffles, stopping at a few playgrounds, eating chips in a cone, etc etc... It is not a cultural hotspot but it is a v relaxing and pleasant place to be for a few days.
Enjoy!