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. Lake Tanganyika is the deepest lake located in central Africa. The savanna has scattered trees and receives enough rain to support drought-resistant plants. The Niger River runs through western Africa and is important to cities like Timbuktu. The Congo River flows through the third largest rainforest in the world. The Nile River is the world's longest river and flows north into the Mediterranean Sea. The Kalahari Desert covers parts of southern Africa and can sustain some animal life.