The Sahara Desert covers the northern regions of Africa, stretching across 13 countries, from the Atlantic Ocean to the Red Sea. It is the largest hot desert in the world; only the frozen waste of the Antarctic is bigger. While the Sahara includes the vast sand dunes commonly seen in movies, it also includes rocky plains, mountains, dried riverbeds and one permanently flowing river -- the Nile. Despite the harsh desert heat, a number of animal species live in the Sahara. However, due to human encroachment, hunting, drought and loss of habitat, several species are on the brink of extinction.