The deepest river in the world, the Congo, has recorded depths in excess of 230m. Its source lies in the mountain highlands of the Easter Rift Valley. The river initially flows northwards before turning south westwards where it enters the Atlantic Ocean. It drains an area over 4.1 million km-2 (1.6 million mi-2). The river and its tributaries makes it an important transportation route across central Africa. However numerous islands, as well as water falls, makes stretches of the river un-navigable. The river has three clear sections, the upper reaches are characterised by lakes, waterfalls and rapids, the middle has a series of Cataracts which end at the Stanley Falls. Finally the lower Congo divides into 2 branches forming large lakes called the Malebo (Stanley) Pool.