The deepest subway in the world
In some cities, the soil is unstable, or tunnels have to be dug deep for strategic purposes. Russia's St. Petersburg Metro has many stations buried more than 50 meters deep, including 9 of the 10 deepest subway stations in Russia (only the second deepest station is the Victory Park Station in Moscow).
The world's deepest subway station, however, is inconclusive. According to public data, the ordnance plant station of Kiev Metro Line 1 in Ukraine is the deepest subway station in the world because it is located in the middle of the mountain and is 105.5 meters away from the surface. However, it is said that the deepest part of the North Korean subway in Pyongyang is 200 meters underground, with an average depth of 100 meters.