Here in London England we find the world's oldest underground system, and one of the longest in terms of route length.

Services began on January 10, 1863 on the Metropolitan Railway; most of the initial route is now part of the Hammersmith City line.

Despite its name, about 55% of the network is above ground.

Popular local names include the Underground and, more colloquially, the Tube (in reference to the cylindrical shape of the system's deep-bore tunnels).

The Underground has 275 stations and runs over 253 miles (408 km) of line.

There are also numerous closed stations.

This is the City Road station, and is relatively inconspicuous from the surface: the only suggestion that a station ever existed is a brick ventilation shaft that incorporates parts of the original station building.