Brussels — or Bruxelles — is highly underrated as a tourist destination. The compact core of the old city is very walkable and it's easy to keep your bearings as the tower on the main square — or Grand Place — is almost always visible, peaking out over nearby buildings.
On your visit to Brussels, you'll find Trappist beer, chocolate, french fries and waffles around every turn. A lot of good stuff comes from Brussels!
For military buffs, the Royal Museum of the Armed Forces is pretty amazing. If you're from America, you'll see a lot of military vehicles that you've likely only seen in the movies, such as a Russian Hind Helicopter or an assortment of MIGs. They even have one of those funny-looking German tanks from Indiana Jones and the Last Crusade.
Brussels may not be a destination city on your bucket list but it's a great central starting point for any European vacation. Spend 2-3 nights in Brussels before heading off to France, Holland, Germany or England and you won't be disappointed!