Metropolitan Line

The Metropolitan line is a London Underground sub-surface railway line, currently running from Aldgate in the City of London to Amersham in Buckinghamshire, with branch lines to Uxbridge, Watford and Chesham. The line is coloured in Transport for London's (TfL) Corporate Magenta on the Tube map and in other branding. Before 1988 the Hammersmith & City line and the East London line were also branded as the Metropolitan line.

When, on 10 January 1863 the Metropolitan Railway opened a line between Paddington and Farringdon, it was the world's first underground railway.

The line is underground for the first 6 miles (9.7 km) from Aldgate to Finchley Road, the rest of the 42-mile (68 km) long line running in the open. Of the 34 stations served, nine are below ground. It is the tenth busiest line on the network with just under 67,000,000 passengers annually. Baker Street is the central London terminus for some trains, others continuing into the City to terminate at Aldgate. The four-track section between Wembley Park and Moor Park allows express or "fast" services to the outer suburbs to overtake slower trains.

The Metropolitan line and the Central line are the only two Underground routes with stations outside the boundaries of Greater London and the M25 orbital motorway.