North Africa's landscape is covered by the world's largest hot desert the Sahara. This massive Arid climate makes it a strange place for a large population of people. Most of the Sahara is too harsh for people to live. The Nile Valley, coastal areas, and the rare oases (plural for oasis) provide the only places that can support life. An oasis is an area of natural water in a desert that allows plant life. The Nile is the world’s longest river. It flows north through the Sahara creating a long oasis in the desert eventually dumping into the Mediterranean Sea. The Nile’s water comes mainly from highland areas near the center of Africa that receives frequent rain, which flows north, downhill into the Nile. The Nile is divided into sections by cataracts. A cataract is a rocky area that creates a waterfall or rapids. There are six cataracts in the Nile river.