The Museum of Musical Instruments is an interesting place to visit for Mr. Sax's failed versions of the saxophone alone. It is also housed in a fantastic art nouveau building: http://www.mim.fgov.be/ (as is the Museum of Cartoons: http://www.comicscenter.net/).

I second a previous poster's comments about the Sablon. A nice area to wander around, especially the antiques shops on Rue Haute and Rue Blaes. Theer's a very nice restaurant called Lola (French style food -- not moules frites) on the Place du Grand Sablon that i can particularly recommend.

If you're into fashion Rue Antoine Daensart and around are pretty cool. For art the Musées royaux des Beaux-Arts has a brilliant collection of Flemish art (some fantastic Bruegels) and the nearby (and similar sounding) Palais des Beaux-Arts has some usually interesting contemporary art exhibitions in a Horta designed building: http://www.bozar.be/home.php?lng=en

It's easy to visit Parliament (http://www.europarl.eu.int/parliamen...=50&pageRank=2) but the Commission is difficult (you need to apply months in advance: http://europa.eu.int/comm/dgs/educat...index_en.html). And why would you? In spite of the Berlaymont's facelift it's still just an office building. If you are in the EU Quarter be sure to go to Maison Antoine.

And finally -- I love the Atomium -- unfortunately it won't re-open until next year (http://www.atomium.be/HTMLsite/dyn/eindex.html).