31. London Underground

Deep beneath London runs a complex network of many miles of tunnels; and, while traffic congests the roads above, hundreds of trains run through these iron and concrete arteries, carrying millions of people into, around, and out of the City. Here is the story of the “Tube”, the world’s first underground railway, which holds London together–from its opening in January 1863, through its deep-level expansion and electrification, to the fully automated trains of the 21st Century’s Jubilee Line.