The City of Paris' administrative limits form a horizontal oval centred on its historical-heart Île de la Cité island; this island is near the peak of an arc of Seine river that divides the city into southern Rive Gauche (Left Bank) and northern Rive Droite regions. Paris is but the core of a built-up area that extends well beyond its limits: commonly referred to as the agglomération Parisienne, and statistically as a unité urbaine (a measure of urban area), the Paris agglomeration's 10,601,122 2013 population makes it the largest urban area in the European Union.[3] City-influenced commuter activity reaches well beyond even this in a statistical aire urbaine de Paris (a measure of metropolitan area), that had a 2013 population of 12,405,426,[7] a number one-fifth the population of France,[8] and one that makes it, after London, the second largest metropolitan area in the European Union. The 2016 Metropole of Grand Paris initiative, encompassing the City of Paris and its surrounding petite couronne department communes, or area covering 814 square kilometers and representing a population of 7 million,[9][10] aims to improve city-suburb cooperation through a unique governing body