What is the colloquial name for the London Underground?

The London Underground is colloquially known as “The Tube.” The nickname comes from the narrow, cylindrical deep-level tunnels built for London’s early underground electric railways.

London’s first underground passenger railway opened in 1863, when the Metropolitan Railway began running between Paddington and Farringdon. Those original tunnels were constructed close to the surface using the cut-and-cover method. Later routes were bored much deeper, using circular tunnels that resembled tubes and required smaller trains. The name gradually spread from these deep-level lines to the entire Underground system.

“The Tube” and “the Underground” are often used interchangeably, but the network includes more than deep tube lines. Several routes, including the Metropolitan, District, Circle and Hammersmith & City lines, use larger trains and shallow cut-and-cover tunnels. Despite its name, only about 45% of the network is actually underground.

The London Underground now has 11 lines and serves Greater London plus parts of several neighboring counties. It remains one of the world’s most recognizable urban transport systems.