
Secret underground: London's disused tube stations are put in the spotlight in a new book, "Hidden London: Discovering the Forgotten Underground."

Immersive journey: The book features new photography of disused stations such as Aldwych, which has has been closed since 1917.

Historic system: The London Underground is the oldest subterranean railway network in the world.

Forgotten sites: The sealed tunnel entrance that leads from King William Street station, the oldest disused deep tube station in London.

Cool down: This lift shaft at Piccadilly Circus was converted to into to ventilation shaft after escalators were fitted at the station in the 1920s.

Lost tunnels: Sections of the old Moorgate station in the City of London were also converted to provide ventilation to the transport network.

Intricate details: This tiled wall in a disused section at Piccadilly Circus station is stamped with the supplier's mark of W.B. Simpson & Sons, London, and made by Maw and Company.

Secret messages: A shrine to St. Barbara, the patron saint of tunnelers, is often found in underground construction sites. This statue at Bank station is marked with the words "pray for bonus."

Protected passageways: The Edwardian ticket hall tiling design at non-operational York Road station, located between King's Cross and Caledonian Road, has been very well preserved.

Steep approach: The original gradient markers on this tunnel under the Thames are still visible.

Strange markings: This marking at Down Street station was formed due to the air flow in tunnels, which can sometimes direct water, creating unusual patterns.

Behind the scenes: This lift shaft at Baker Street station has been out of action since the 1940s.

Empty shafts: A redundant fan impeller located in a dark corner of disused York Road station.

Underground expeditions: London Transport Museum has been running tours of many of the disused stations across the city since the 1970s.

Secret world: St. Mary's was one of several stations where disused platforms were converted and used as civilian shelters during World War II.

Inventive transformation: The exterior of South Kentish Town station, which closed in 1924, has been transformed into a shop.

Hidden spaces: Passengers can sometimes spot glimpses of disused stations while traveling on the tube.

Deserted halls: Aldwych station opened to the public in 1907, but closed almost a century later.

Abandoned station: The interior of one of the original Otis lifts at Aldwych.

Repurposed facade: A former entrance to Hyde Park Corner station has been transformed into boutique hotel The Wellesley.