Jakarta lies in a low and flat alluvial plain, ranging from  with an average elevation of  above sea level with historically extensive swampy areas. Some parts of the city have been constructed on reclaimed tidal flats that occur in around the area. Thirteen rivers flow through Jakarta. They are Ciliwung River, Kalibaru, Pesanggrahan, Cipinang, Angke River, Maja, Mookervart, Krukut, Buaran, West Tarum, Cakung, Petukangan, Sunter River and Grogol River. They flow from the Puncak highlands to the south of the city, then across the city northwards towards the Java Sea. The Ciliwung River divides the city into the western and eastern districts.