Oka

The Oka 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 to the town of Kaluga. Its length is 1,500 km and its catchment area is 245,000 km2. The Russian capital Moscow sits on one of the Oka's tributaries—the Moskva.