The major geographical features of Africa include the Sahara Desert, the largest desert in the world. The Atlas Mountains run along northern Africa between the Mediterranean Sea and Sahara. The Sahel is the transitional land between the desert and savanna regions that receives more rain than the desert. Lake Tanganyika is the deepest lake located in central Africa. The savanna grasslands contain scattered trees and receive enough rain to support drought-resistant plants. The Niger River runs through western Africa and is an important water source. The Congo River flows through the third largest rainforest in the world. The Drakensberg Mountains are the highest in southern Africa. The Nile River is the world's longest river and flows north into the Mediterranean.