Ethiopia contains a variety of distinct topographical zones. It is a country of geographical contrasts, varying from as much as 116 m (381 ft) below sea level in the Danakil depression to more than 4,600 m (15,000 ft) above in the mountainous regions. Ras Dashen, with an altitude of 4,620 m (15,158 ft), is the fourth-highest peak in Africa. The most distinctive feature is the northern part of the Great Rift Valley, which runs through the entire length of the country in a northeast-southwest direction, at a general elevation of 1,500 to 3,000 m (4,900–9,800 ft). Immediately to the west is the High Plateau region; this rugged tableland is marked by mountain ranges. East of the Great Rift Valley is the Somali Plateau—arid and rocky semidesert, extending to the Ogaden, which covers the entire southeastern section of the country. In the north, the Denakil Desert reaches to the Red Sea and the coastal foothills of Eritrea. The western boundary of Ethiopia follows roughly the western escarpment of the High Plateau, although in some regions the Sudan plains extend into Ethiopian territory. Also part of Ethiopia is the Dahlak Archipelago in the Red Sea.
Ethiopia's largest lake, Lake T'ana, is the source of the Blue Nile River. This river, which winds around in a great arc before merging with the White Nile in the Sudan, travels through great canyons, which reach depths of more than 1,200 m (4,000 ft). Several rivers in the southwest also make up a system of tributaries to the White Nile.