London is home to the world's oldest surviving underground railway, the London Underground.
The Metropolitan Railway opened on 10 January 1863 between Paddington and Farringdon. It was built to relieve congestion on London's crowded streets and used steam locomotives in its early years. The railway later became part of the expanding network known as the London Underground.
London's system is commonly nicknamed the Tube, although not all of its lines run through circular deep-level tunnels. The network includes both deep underground routes and cut-and-cover sections built close to the surface.
The Underground's famous map was redesigned by Harry Beck in the 1930s. His diagram used straight lines and regular angles, sacrificing geographic accuracy for clarity. The system has become both a major transport network and a recognizable symbol of London, with stations serving much of Greater London and nearby areas.