In the three nations, the Regional park covers some 10,000 km2 (3,900 sq mi) largely uninhabited by humans, having been until the 1970s a Malarial zone of wetlands formed by the delta of the Mekrou River with the Niger, broken by rocky hills. Historically, the area has been at one time a major area of human habitation, judged by the important archaeological sites (mostly tombs) found in the area.