Central line (London Underground) Central line (London Underground) The Central line is a London Underground line that runs through central London, from , Essex, in the north-east to and in the west. Coloured red on the Tube map, the line serves 49 stations over , which makes it the longest Tube line. It is also 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, Central line trains are smaller than those on British main lines. The line was opened as the Central London Railway in 1900, crossing
London a major international air transport hub with the busiest city airspace in the world. Eight airports use the word "London" in their name, but most traffic passes through six of these. Additionally, various other airports also serve London, catering primarily to general aviation flights. The London Underground, commonly referred to as the Tube, is the oldest and third longest metro system in the world. The system serves 270 stations and was formed from several private companies, including the world's first underground electric line, the City and South London Railway. It dates from 1863. Over four million journeys are made every