Eat, Drink, and Be Merry. Beer and fries is really the classic combination and there's no better place to taste the two than Brussels.
Rub Shoulders With Diplomats. The "capital of Europe" plays host to the vast bureaucracy of the European Union institutions—the European parliament, Council, and Commission.
Be a High Culture Vulture. Home to the Musée des Instruments de Musique (MIM), Centre Belge de la Bande Dessinée, Brussels's comic strip museum, and the Musée d'Art Ancien, just to name a few, you could spend all your times soaking up the sights. There's even a EUR 15 combo pass to help you do it.
To Market, To Market. Every day of the week guarantees at least one lively market where stalls sell everything from olives and fruit to antique furniture and dog-eared books.