Details: This poster is of a map for the London Underground.
The London Underground is a transit system that serves a large part of Greater London and some neighbouring areas. It is the world's oldest underground system, and is one of the longest in terms of route length. Services began on 10 January 1863 on the Metropolitan Railway. Despite its name, about 55% of the network is above ground. Popular local names include the Underground, more colloquially the Tube.