The District line is a major line of the London Underground, serving the city of London and its surrounding areas. It runs from Upminster in the east to Ealing Broadway and Richmond in the west, covering a distance of approximately 40 kilometers. The line is known for its distinctive green color on the Tube map and connects several key areas, including Westminster, Kensington, and Wimbledon. Opened in 1868, the District line is one of the oldest lines in the London Underground network. It operates both above and below ground, with a mix of modern and historic trains. The line is an essential part of London's public transport system, providing access to various attractions, including the Houses of Parliament and Kew Gardens.