The Amur, Neva, Lena, Volga, Ural, and Oka are all rivers located in Russia. The Amur is the longest river in the country, stretching over 2, 800 miles from its source in the mountains of Mongolia to its mouth on the Sea of Okhotsk. The Neva is a major river in northwestern Russia, flowing through St. Petersburg and emptying into the Gulf of Finland. The Lena is the 11th longest river in the world, originating in the Baikal Mountains and flowing 4, 400 miles to the Laptev Sea. The Volga is the longest river in Europe, flowing through central Russia and emptying into the Caspian Sea. The Ural River is a major river in western Russia, flowing 1, 500 miles from the Ural Mountains to the Caspian Sea. The Oka is a major tributary of the Volga, originating in the Central Russian Upland and flowing south to join the Volga near Nizhny Novgorod.