Located in the center of Belgium is the capital city of Brussels. The city is the home of the Royal Family as well as important international organizations that include the headquarters for NATO, the Western European Union, and EUROCONTROL. The city center is comprised of a Lower Town and Upper Town that are surrounded by numerous suburbs. Brussels is a surprisingly modern city and known as the "capital of Art Nouveau" for the numerous Art Nouveau buildings here, some of which are now a UNESCO World Heritage Site. Brussels has many World Heritage Sites, including the historical city center and the big Market Square.