Brussels is not a large town with a lot of 'highlights' to see; nevertheless, it is possible to enjoy a nice time while there.

In addition to the Atomium, you easily could spend the better part of a day strolling around the old part of Brussels around the big market place (Grand Place), which some claim to be the most beautiful in the world. There are many quaint streets in that neigbourhood, nice galleries, (covered streets), etc...

Enjoy "a Golden" (a very light aperitif) in the Chaloupe d'Or (The golden Boat) in the Grand Place. It is a nice, even romantic place to while away some free time. If you would like to sample a serious Belgian Beer, try a Duvel.

Apart from this, I would suggest boarding a train to Leuven (~15 minutes), which is a very young feeling university town with many old buildings, streets, etc. Similarly, Gent and Antwerp are ~30 minutes away, and Bruges is 45 minutes distant. The train service is very unlike that of England (and Scotland?), as they are reliable (and frequent).

David