Haiti has many mountains. There are only some coastal plains and few valleys. The largest valley is the "Cul-de-Sac". Port-au-Prince is in the western end of this valley. The country's main river is the Artibonite, which is also the longest in Hispaniola. Haiti's biggest city is Port-au-Prince, with more than 3 million people in its metropolitan area. The second largest city is Cap-Haïtien.