Belgium is a sovereign state and a federal constitutional monarchy with a parliamentary system. Its institutional organization is complex and is structured on both regional and linguistic grounds. It is divided into three highly autonomous regions: the Flemish Region (Flanders) in the north, the Walloon Region (Wallonia) in the south, and the Brussels-Capital Region. Brussels is the smallest and most densely populated region, as well as the richest region in terms of GDP per capita.