Tube map in the context of "Circle line (London Underground)"

London Overground (also known simply as the Overground) is a suburban rail network serving London and its environs. Established in 2007 to take over Silverlink Metro routes, it now serves a large part of Greater London as well as Hertfordshire, with 113 stations on the six lines that make up the network.

The Overground forms part of the United Kingdom's National Rail network but it is under the concession control and branding of Transport for London (TfL). Operation has been contracted to Arriva Rail London since 2016. TfL previously assigned orange as a mode-specific colour for the Overground in branding and publicity including the roundel, on the Tube map, trains and stations.

The District line is a London Underground line running from Upminster in the east and Edgware Road in northwestern Central London to Earl's Court in west London, where it splits into multiple branches. One branch runs to Wimbledon in south-west London and a short branch, with a limited service, only runs for one stop to Kensington (Olympia). The main route continues west from Earl's Court to Turnham Green after which it divides again into two western branches, to Richmond and Ealing Broadway.

Printed in green on the Tube map, the line serves 60 stations (more than any other Underground line) over 40 miles (64 km). It is the only Underground line to use a bridge to traverse the River Thames, crossing on both the Wimbledon and Richmond branches. The track and stations between Barking and Aldgate East are shared with the Hammersmith & City line, and between Tower Hill and Gloucester Road and on the Edgware Road branch they are shared with the Circle line. Some of the stations between South Kensington and Ealing Common are shared with the Piccadilly line. Unlike London's deep-level lines, the railway tunnels are just below the surface, and the trains are of a similar size to those on British main lines.

The Hammersmith & City line is a London Underground line that runs between Hammersmith in west London and Barking in east London. Coloured pink on the Tube map, it serves 29 stations over 15.8 miles (25.5 km). Between Farringdon and Aldgate East it skirts the City of London, the capital's financial heart, hence the line's name. Its tunnels are just below the surface and are a similar size to those on British main lines. Most of the track and all stations are shared with the Circle, District or Metropolitan lines. Over 141 million passenger journeys are made each year on the Hammersmith & City line.

In 1863, the Metropolitan Railway began the world's first underground railway service between Paddington and Farringdon with wooden carriages hauled by steam locomotives. The following year, a railway west from Paddington to Hammersmith was opened and this soon became operated and owned jointly by the Metropolitan and Great Western Railway companies. The line was then extended to the east, in stages, reaching the East London Railway in 1884. The line was electrified in 1906, and, in 1936, after the Metropolitan Railway had been absorbed by the London Passenger Transport Board, some Hammersmith & City line trains were extended over the former District Railway line to Barking. The Hammersmith & City route was shown on the Tube map as part of the Metropolitan line until 30 July 1990, when it was redesignated as a separate line.

The Metropolitan line, colloquially known as the Met, is a London Underground line between Aldgate in the City of London and Amersham and Chesham in Buckinghamshire, with branches to Watford in Hertfordshire and Uxbridge in Hillingdon. Printed in magenta on the tube map, the line is 41.4 miles (66.7 km) long and serves 34 stations. Between Aldgate and Finchley Road, the track lies mostly in shallow "cut and cover" tunnels, apart from short sections at Barbican and Farringdon stations. The rest of the line is above ground, with a loading gauge similar to those of main lines. Almost 94 million passenger journeys were made on the line in 2019.

This line is one of two Underground lines that cross the Greater London boundary and proceed outwards into the Home Counties, the other being the Central line. It is the only Underground line with an express service at peak times; the longer distance between stations means trains can achieve the system's highest speeds, up to 62 miles per hour (100 km/h), on some sections.

The Northern line is a London Underground line that runs between North London and South London. It is printed in black on the Tube map. It carries more passengers per year than any other Underground line – around 340 million in 2019 – making it the busiest tube line in London. The Northern line is unique on the network in having two routes through Central London, two northern branches and two southern branches. Despite its name, it does not serve the northernmost stations on the Underground, though it does serve the southernmost station at Morden, the terminus of one of the two southern branches.

The line's northern termini, all in the London Borough of Barnet, are at Edgware and High Barnet; Mill Hill East is the terminus of a single-station branch line off the High Barnet branch. The two main northern branches run south to join at Camden Town where two routes, one via Charing Cross in the West End and the other via Bank in the City, continue and then join at Kennington in Southwark. At Kennington the line again divides into two branches, one to each of the southern termini – at Morden, in the borough of Merton, and at Battersea Power Station in Wandsworth.

The Central line is a London Underground line that runs between West Ruislip or Ealing Broadway in the west, and Epping or Woodford via Hainault in the north-east, via the West End, the City, and the East End. Printed in red on the Tube map, the line serves 49 stations over 46 miles (74 km), making it the network's longest line. It is one of only two lines on the Underground network to cross the Greater London boundary, the other being the Metropolitan line. One of London's deep-level railways traversing narrow tunnels, Central line trains are smaller than those on British main lines.

The line was opened as the Central London Railway in 1900, crossing central London on an east–west axis along the central shopping street of Oxford Street to the financial centre of the City of London. It was later extended to the western suburb of Ealing. In the 1930s, plans were created to expand the route into the new suburbs, taking over steam-hauled outer-suburban routes to the borders of London and beyond to the east. These projects were mostly realised after the Second World War, when construction stopped and the unused tunnels were used as air-raid shelters and factories. However, suburban growth was limited by the Metropolitan Green Belt: of the planned expansions one (to Denham, Buckinghamshire) was cut short and the eastern terminus of Ongar ultimately closed in 1994 due to low patronage; part of this section between Epping and Ongar later became the Epping Ongar Railway. The Central line has mostly been operated by automatic train operation since a major refurbishment in the 1990s, although all trains still carry drivers. Many of its stations are of historic interest, from turn-of-the-century Central London Railway buildings in west London to post-war modernist designs on the West Ruislip and Hainault branches, as well as Victorian-era Eastern Counties Railway and Great Eastern Railway buildings east of Stratford, from when the line to Epping was a rural branch line.

The Piccadilly line is a deep-level London Underground line which runs between the west and the north of London with 53 stations on the line. The line serves Heathrow Airport, and some of its stations are near tourist attractions in Central London such as King's Cross, Piccadilly Circus and Buckingham Palace. It has two western branches which split at Acton Town, with the main one towards Heathrow Airport terminals and the other northern branch towards Uxbridge. The District and Metropolitan lines share some sections of track with the Piccadilly line. The line is printed in dark blue (officially "Corporate Blue", Pantone 072) on the Tube map. It is the sixth-busiest line on the Underground network, with nearly 218 million passenger journeys in 2019.

The first section, between Finsbury Park and Hammersmith, was opened in 1906 as the Great Northern, Piccadilly and Brompton Railway (GNP&BR). The station tunnels and buildings were designed by Leslie Green, featuring ox-blood terracotta facades with semi-circular windows on the first floor. When Underground Electric Railways of London (UERL) took over the line, it was renamed the Piccadilly line. Subsequent extensions were made to Cockfosters, Hounslow West and Uxbridge in the early 1930s, when many existing stations on the Uxbridge and Hounslow branches were rebuilt to designs by Charles Holden of the Adams, Holden & Pearson architectural practice. These were generally rectangular, with brick bases and large tiled windows, topped with a concrete slab roof. The western extensions took over certain existing District line services, which were fully withdrawn in 1964.

The Victoria line is a London Underground line that runs between Brixton in South London, and Walthamstow Central in the east, via the West End. It is printed in light blue on the Tube map and is one of the only two lines on the network to run completely underground, the other being the Waterloo & City line.

The line was constructed in the 1960s and was the first entirely new Underground line in London for 50 years. It was designed to reduce congestion on other lines, particularly the Piccadilly line and the Charing Cross branch of the Northern line. The first section, from Walthamstow Central to Highbury & Islington, opened in September 1968 and an extension to Warren Street followed in December. The line was completed to Victoria station in March 1969 and was opened by Queen Elizabeth II who rode a train from Green Park to Victoria. The southern extension to Brixton opened in 1971, and Pimlico (the only station in the line without an interchange) was added in 1972.