Congo lies astride the equator, and virtually all of the country is part of the vast Congo River drainage basin. North central Congo is made up of a large plateau (average elevation: c.1,000 ft/300 m), which is covered with equatorial forest and has numerous swamps. The plateau is bordered on the east by mountains, which rise to the lofty Ruwenzori range (located on the border with Uganda). The Ruwenzori include Margherita Peak (16,763 ft/5,109 m), the country's highest point; they are situated in the western or Albertine branch of the Great Rift Valley, which runs along the entire eastern border of the country and also takes in lakes Albert, Edward, Kivu, and Tanganyika. In S Congo are highland plateaus (average elevation: c.3,000 ft/910 m; highest elevation: c.6,800 ft/2,070 m), which are covered with savanna. The high Mitumba Mts. in the southeast include Lake Mweru (situated on the border with Zambia). In addition to Kinshasa, the major urban areas include Boma, Kalemie, Kamina, Kananga, Kisangani, Kolwezi, Likasi, Lubumbashi, Matadi, Mbandaka, and Mbuji-Mayi.
The population of Congo comprises approximately 450 ethnic groups, the great majority of whom speak one of the Bantu languages. In addition, there are Nilotic speakers in the north near Sudan and scattered groups of Pygmies (especially in the Ituri Forest in the northeast). The principal Bantu-speaking ethnic groups are the Kongo, Mongo, Luba, Bwaka, Kwango, Lulua, Lunda, and Kasai. The Alur are the main Nilotic speakers. In the 1990s, Congo also had an influx of immigrants, particularly refugees from neighboring countries. In 1985 over half the population was rural, but the country is becoming increasingly urbanized.
French is Congo's official language, but it is spoken by relatively few persons. Swahili is widely used in the east, and Lingala is spoken in the west; Tshiluba is also common. About 50% of the inhabitants are Roman Catholics and 20% are Protestants. A substantial number are adherents of Kimbanguism, an indigenous Christian church. Many also follow traditional religious beliefs, and about 10% are Muslims.