Brussels, Flemish Brussel, French Bruxelles, city, capital of Belgium. It is located in the valley of the Senne (Flemish: Zenne) River, a small tributary of the Schelde. Greater Brussels is the country’s largest urban agglomeration. There is plenty about Brussels that makes it like no other city. It’s the capital of the European Union for a start (but you wouldn’t necessarily sense it), operating in two native languages (French and Dutch/Flemish).