Kivu, lake, 1,042 sq mi (2,699 sq km), 55 mi (89 km) long, on the Congo-Rwanda border, E central Africa; highest lake in Africa (4,788 ft/1,459 m). It is drained by the Ruzizi River, which flows S into Lake Tanganyika. Beneath the lake lie vast reserves of methane gas (and carbon dioxide) which have not been exploited; localized natural releases of the gases sometimes asphyxiate individuals. Lake Kivu is a tourist center. Goma, Congo, on the N shore, is subject to the eruptions of nearby Mt. Nyiragongo.