Benin falls into four main geographic regions. In the south is a narrow coastal zone (1–3 mi/1.6–4.8 km wide) fringed on the north by a series of interconnected lagoons and lakes with only two outlets to the sea (at Grand-Popo and Cotonou). Behind the coastal region is a generally flat area of fertile clay soils; this is crossed by the wide Lama marsh, through which flows the Ouémé River. In NW Benin is a region of forested mountains (the Atacora; highest point c.2,150 ft/655 m), from which the Mekrou and Pendjari rivers flow NE to the Niger River (which forms part of the country's northern border). In the northeast is a highland region covered mostly with savanna and containing little fertile soil.
Although there are 42 ethnic groups in Benin, its population is divided into four main ethnolinguistic groups—Fon, Yoruba, Voltaic, and Fulani. The Fon-speakers, who live in the south, include the Fon, or Dahomey (Benin's largest single ethnic group), Aja, Peda, and Chabe subgroups. The Yoruba live in the southeast near Nigeria, the group's main homeland. The Voltaic-speakers live in central and N Benin and include the Bariba and Somba subgroups. The Fulani live in the north. French is the country's official language; Fon, Yoruba, and other indigenous tongues are also spoken. About a third of the inhabitants follow traditional religious beliefs; voodoo originated here some 350 years ago but was only officially recognized in 1996. About 43% are Christian (largely Roman Catholic) and 25% (living mostly in the north) are Muslim. Benin's population is concentrated in the southern portion of the country and in rural areas.