It's a good city for just wandering in -- some lovely buildings and nice parks. There's a walking tour of the cartoon murals in one of my guidebooks I can lend you. It might be a bit out of date, however.
The Fine Art Museum is great -- lots of lovely Breughels and Magrittes. Except it's closed until 23rd March <!-- s:( --><img src="{SMILIES_PATH}/icon_sad.gif" alt="

" title="Sad" /><!-- s:( -->
The Comics Museum[/url:2l4ucykc] looks great, though I've never been.
There's beer as well. And chocolate. And beer.