The Sahara is bordered by the Atlantic Ocean on the western edge, the Atlas Mountains and the Mediterranean Sea to the north, the Red Sea on the east, and the Sudan and the valley of the Niger River on the south. The Sahara is divided into western Sahara, the central Hoggar (Ahaggar) Mountains, the Tibesti Mountains, the Air Mountains, an area of desert mountains and high plateaus, Ténéré desert and the Libyan desert, which is the most arid region.