The London Underground is celebrating its 150th anniversary. It was the world's first underground railway.
Its first stretch of track between Paddington - Farringdon was unveiled on 9 January, 1863, with passengers making their first journeys on the Metropolitan Railway a day later.
The Underground now carries four million passengers per day. The network extends 402km and a record 1.171 billion passenger journeys were made in 2011/12, AAP reports.
AAP reports a series of events are planned to mark the milestone, including trips by steam trains through Tube tunnels and two new two-pound coins commemorating the anniversary.
Twelve short stories by well-known authors will each focus on one Tube line, and more broadly on what the Underground means to Londoners and visitors.
The original Underground, opened after just three years' construction, was designed to reduce congestion above ground from carts and stagecoaches.
Today the Underground employs 19,000 people and carries passengers between 270 stations each year, linking London with its commuter belt including Surrey, Kent, Essex and Hertfordshire.
Latest innovations include air-conditioned trains and high-frequency services planned on the Victoria and Central lines.
Waterloo is the busiest station, with 82 million passengers passing through each year.
During World War II, 175,000 people sheltered in underground stations from the bombings.
The Tube also bore the impact of terrorist attacks in July 2005 which killed 56 people on three tube lines and a bus.
A huge fire left 31 people dead in 1987 at King's Cross Station, leading to a safety overhaul and smoking ban.
London Mayor Boris Johnson calls the Tube "arguably the best underground system in the world".
"The arrival of the Tube was truly revolutionary and today it is still admired around the world,'' he said.
"It annihilates distance, liquidates traffic and is the throbbing cardiovascular system of the greatest city on earth.
"It continues to play a hugely important role in the success of our capital - efficiently moving record numbers of people during the London 2012 Games."