Tower Subway: The Tube London Built and Forgot

Beneath the pavement at Tower Hill, a few metres from the entrance to the Tower of London, sits a small brick drum that millions of tourists walk past every year without a second glance. It marks the entrance to the Tower Subway, built in 1870, the world's first tube railway, a tunnel that carried a million pedestrians a year through a seven-foot iron tube under the Thames, survived a direct German bomb, and is now owned by Vodafone. The tunnel that everyone forgot built the system that everyone uses.