The Moscow Metro is a rapid transit system serving Moscow, Russia and the neighbouring Moscow Oblast towns of Krasnogorsk, Reutov and Kotelniki. Opened in 1935 with one line and 13 stations, it was the first underground railway system in the Soviet Union. As of 2015, the Moscow Metro has 199 stations and its route length is . The system is mostly underground, with the deepest section underground at the Park Pobedy station, one of the world's deepest. As of 2013, the Moscow Metro is the busiest metro system outside of Asia and the 6th longest in the world.