At the dead of night, the photographer – known to his Instagram followers as Dark Cyanide – heads out to look for hidden gems, like abandoned stations, provisions and tunnels. His intriguing images feature vibrant streaks, graffiti, and tight framing – and by adding individuals to some to some of shots, he is also able to depict the incredible scale of some of the tunnels. Here: Unnamed subway track in New York City. (Photo by Dark Cyanide/Caters News)

A woman sits in a train at a subway station in Pyongyang, North Korea on September 11, 2018. (Photo by Danish Siddiqui/Reuters)

Paramedics carry an injured woman out from a subway station after a rush-hour subway train derailment, to be transported by a medical helicopter in Moscow, Russia, on Tuesday, July 15, 2014. A rush-hour subway train derailed in Moscow Tuesday, killing 20 people and injuring at least 150, emergency officials said. Several cars left the track in the tunnel after a power surge triggered an alarm, which caused the train to stop abruptly. (Photo by Ivan Sekretarev/AP Photo)

Commuters walk up the redesigned subway stairs at the Tanjong Pagar subway station on August 23, 2011 in Singapore. The subway stairs have been repainted in bright colours and slogans encouraging people to take the stairs, by way of promoting fitness in the city. (Photo by Chris McGrath/Getty Images)

Runners warm up during the Team Pants And Bra photcall at City Hall on January 26, 2012 in London, England. Team Pants and Bra sprinted through central London this morning, encouraging fellow runners to join TeamPB and proudly wear pants and bras for the Virgin London Marathon in April, representing The Prostate Cancer Charity and Breast Cancer Care. (Photo by Ian Gavan/Getty Images for Prostate Cancer)

“Monorail Subway, Capitol To Senate. The Car. Senators Swanson And Townsend As Passengers, 1916”. (Photo by Harris & Ewing Collection). (Please click to enlarge)

New York City policemen tangled with demonstrators at a subway station on the opening day of the New York World's Fair, April 22, 1964. Youths attempted to stall the train, which was headed from the city to the fairgrounds, as a form of protest on behalf of civil rights for blacks. (Photo by Charles Gorry/AP Photo)

Performers take part in a parade during the annual Cervantes market (Mercado Cervantino) in the hometown of famous Spanish writer Miguel de Cervantes, Alcala de Henares, Spain, October 9, 2015. The Mercado Cervantino, which represents a market and fair from the 16th and 17th centuries, takes place in the city's historic centre and commemorates Miguel de Cervantes' baptism, which took place on October 9, 1547. (Photo by Susana Vera/Reuters)