ST PETERSBURG - JUNE 20: Passengers entering and leaving a subway train at station Zvenigorodskaya, June 20, 2011, St. Petersburg, Russia. The Saint Petersburg Metro is the deepest subway system in the world by the average depth of all the stations.

Editorial Use Only: This image can only be used for editorial purpose. Use of this image in advertising, commercial or for promotional purposes is prohibited unless additional clearances are secured by the licensee. 123RF.com does not provide any clearance services.