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 (French: Escaut). Greater Brussels is the country’s largest urban agglomeration. It consists of 19 communes, or municipalities, each with a large measure of administrative autonomy. The largest commune—which, like the greater metropolitan area, is named Brussels—contains the historic core of the city and the so-called “European Quarter,” where the institutions of the European Union (EU) are located.