London Underground with smaller trains that run in two circular tunnels ("tubes") with a diameter about . These lines have the exclusive use of a pair of tracks, except for the Piccadilly line, which shares track with the District line between Acton Town and Hanger Lane Junction and with the Metropolitan line between Rayners Lane and Uxbridge; and the Bakerloo line, which shares track with London Overground services north of Queen's Park. Fifty-five per cent of the system runs on the surface. There are of cut-and-cover tunnel and of tube tunnel. Many of the central London underground stations on deep-level tube routes
Line C (Buenos Aires Underground) Line C (Buenos Aires Underground) Line C of the Buenos Aires Underground, that runs from Retiro to Constitución terminus, opened on 9 November 1934, and it has a length of . It runs under such streets as Lima Sur, Bernardo de Irigoyen, Carlos Pellegrini, Esmeralda, la Plaza San Martín and Avenida Ramos Mejia. It not only connects to every other line on the system (with the exception of Line H, which will be connected at a later date), but its termini at Retiro and Constitución also connect it to some of the most important commuter rail networks in Buenos Aires,