Oka
The 99th longest river in the world
The Oka (UK, US, [ɐˈka]) is a river in central Russia, the largest right tributary of the Volga. It flows through the regions of Oryol, Tula, Kaluga, Moscow, Ryazan, Vladimir and Nizhny Novgorod and is navigable over a large part of its total length, as far upstream as the town of Kaluga. Its length is 1,500 km (930 mi) and its catchment area 245,000 km2 (95, 000 sq mi). The Russian capital Moscow sits on one of the Oka's tributaries—the Moskva, from which the capital's name is thought to be derived.
Flows through: Russia.
River data from Wikidata (CC0); lengths normalised to a common unit.