The London Underground is a rapid transit system serving a large part of Greater London and neighbouring areas of Essex, Hertfordshire and Buckinghamshire in the UK. With its first section opening in 1863, it was the first underground railway system in the world. In 1890 it became the first to operate electric trains. Despite the name, about 55% of the network is above ground. It is usually referred to officially as 'the Underground' and colloquially as the Tube, although the latter term originally applied only to the deep-level bored lines, along which run slightly lower, narrower trains along standard-gauge track, to distinguish them from the sub-surface "cut and cover" lines that were built first. More recently this distinction has been lost and the whole system is now referred to as 'the Tube', even in recent years by its operator in official publicity.
Liverpool Street railway station it is one of the busiest stations in the United Kingdom, the third busiest in London after Waterloo and Victoria with 123 million visitors each year. Liverpool Street is one of seventeen stations directly managed by Network Rail. The station has exits to Bishopsgate, Liverpool Street and the Broadgate development. The station connects the Central Line, Circle Line, Metropolitan Line, and Hammersmith & City Line. The station is in Travelcard zone 1.