Kolyma (kŏlĭmäˈ, kōlēˈmə, Rus. kəlĭˈmə) [key], river, c.1,500 mi (2,410 km) long, rising in several headstreams in the Kolyma and Cherskogo ranges, Russian Far East. It flows generally N to the Arctic Ocean at Nizhniye Kresty. It is navigable (June–October) for c.1,000 mi (1,610 km). Its upper course crosses the rich Kolyma Gold Fields, which supplied much of the gold for Soviet foreign trade. Gold mining was begun in the 1930s, and both the fields and the surrounding area were developed using the labor of prisoners from Stalin's Gulag. The Kolyma Range (or Gyda Range), E of the Kolyma River, extends NE from Magadan and rises to c.6,000 ft (1,830 m).