A little known tunnel, the deepest in London, runs through the heart of the city for more than four miles at a depth of 80 metres and does an unpleasant but crucial job.
Beneath London's streets, there's a whole network of tunnels used for the Tube as well for water and sewage that are out of sight and mind, reports MyLondon.
There's the London Underground network that spans 402km across the city, in winding tunnels with the deepest point on the Tube at Hampstead station, where it is 58.5 metres below the ground.
