Mainland Tanzania falls into three major geographical zones—a narrow lowland coastal strip along the Indian Ocean; a vast interior plateau; and a number of scattered mountainous regions. The coastal zone (10–40 mi/16–60 km wide) receives considerable rainfall and has much fertile soil. The plateau (average elevation: 3,500–4,500 ft/1,070–1,370 m) extends over most of the interior and is cut in two places by branches of the Great Rift Valley. The western branch contains Lake Tanganyika and the eastern branch runs through central Tanzania about 500 ft (150 m) below the level of the plateau; the two branches merge just north of Lake Nyasa. The plateau receives little rainfall, but in most parts there is enough to support agriculture.
The Serengeti National Park, one of the country's several wildlife reserves, is east of Lake Victoria, and Lake Rukwa is in the southwest. The mountainous regions include Mt. Meru (14,979 ft/4,566 m) and Mt. Kilimanjaro (19,340 ft/5,895 m, the highest point in Africa) in the northeast; the Usambara, Nguru, and Uluguru mts. in the east; the Livingstone Mts. and the Kipengere Range near Lake Nyasa in the south; and the Ufipi Highlands in the southwest. Tanzania's few rivers include the Pangani, the Rufiji, and the Ruvuma (which forms part of the border with Mozambique), all of which flow into the Indian Ocean, and the Malagarasi River, which flows into Lake Tanganyika. In addition to Dar-es-Salaam and Dodoma, other important towns on the mainland include Arusha, Iringa, Kigoma, Morogoro, Mbeya, Moshi, Mtwara, Mwanza, Tabora, and Tanga.
The great majority of Tanzania's population is of African descent, and most of the peope speak Bantu languages. There are approximately 130 ethnic groups. Inhabitants of South Asian, European, and Arab descent constitute approximately 1% of the population. The Bantu-speaking peoples include the Sukuma (the republic's largest ethnic group), Bena, Chagga, Gogo, Ha, Haya, Hehe, Luguru, Makonde, Makua, Ngoni, Nyakyusa, Nyamwezi, and Nyaturu. In addition, the Masai speak a Nilotic language; the Sandawe speak a language akin to Khoikhoi; and the Iraqw speak a Cushitic language. The inhabitants of Zanzibar are mainly of Arab, African, or mixed Arab and African descent. Swahili and English are the republic's official languages; Arabic is also spoken, primarily on Zanzibar. About 30% of the mainland population is Christian, while 35% is Muslim, and another 35% follow traditional religious beliefs. The population of Zanzibar is almost completely Sunni Muslim.