Unlike much younger North American cities, Paris does not have a neat and orderly checkerboard street pattern. Furthermore, the large, old trees that line the streets of metropolitan Paris obscure what pattern there is. Most of the population of France is evenly distributed throughout the country; the only exception of concentrated urban population is Paris. With a population of approximately 10 million people, Paris is without rival in France. The Seine River and the two large airports (Charles de Gaulle northeast of the central city and Orly to the south) are the major identifiable features in this near-vertical photograph. The dark areas on the photograph outside the metropolitan areas are forests, and the dark (vegetated) areas in the city are parks. Prominent are the Bois de Boulogne in a downstream loop of the Seine and the Bois de Vincennes near an upstream loop. The original city of Paris was founded in pre-Roman times on an island in the Seine River. Paris is positioned geographically in the Paris Basin, relatively flat terrain that becomes gently rolling hills. The city lies in a large, prosperous agricultural region that has enhanced the development of Paris.