Urban explorer Steve Duncan shares shots from his out-of-bounds expeditions in New York, London, Paris, and other world cities.

[Editor’s note: All photos courtesy of Steve Duncan. All rights reserved.]

Steve Duncan has been an urban explorer for over a decade, first venturing underground as a student at Columbia University in New York City. Since then, he has entered underground worlds across the United States and Europe, including the limestone quarries under Odessa in the Ukraine and caves used to store beer by breweries in St. Paul, Minnesota.

In 2004 and 2005, Duncan hosted the Discovery Channel show Urban Explorers, and he has appeared on the History Channel as an expert on New York City’s underground. Most recently, his expeditions — and his photography — got some press following a week-long expedition into underground Manhattan with Erling Kagge, a Norwegian polar explorer.

What follows is a collection of 20 of his photos of out-of-sight, out-of-mind urban infrastructure — above ground as well as below — from around the world. Make sure to stop by Trips tomorrow for an interview with Steve Duncan.

1

Victorian drainage tunnel, Nottingham England

This tunnel from 1884 was part of England's massive public-health construction projects in the late 19th century.

2

West Side tunnel, NYC

An old freight railroad line, now used by Amtrak, in a tunnel that became home to many from the '70s through the early '90s.

3

Utility tunnels, Stockholm, Sweden

Tunnels through granite bedrock carry utilities underneath Stockholm.

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4

West Side tunnel, NYC

Murals from the era of the large community of "Mole People" that lived in these train tunnels.

5

Fleet River sewer, London

The magnificent brick sewer was built in the mid-19th century around the Fleet River, which had been a vital transportation route for centuries.

6

Paris Catacombs

Taking a break while exploring the catacombs beneath Paris.

7

1964 World's Fair grounds, NYC

Though unused since the fair in 1964, the NY State Pavilion Observation towers in Flushing Meadows, Queens, still give a beautiful view.

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8

Bradford Beck River, Bradford, England

Bradford's development as a wool-processing center ran off water power from streams like the Bradford Beck, which was put underground in the Victorian period.

9

Subway tracks, NYC

A disused subway track, one of many miles in the New York City system.

10

Neglinnaya River, Moscow

The Neglinnaya River, which for centuries served as a sort of moat around the Kremlin, now runs deep underneath Red Square.

11

Paris Catacombs

A self-portrait while exploring the ossuaries of the Paris Catacombs.

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12

Knickerbocker Sewer, NYC

One of the largest sewers in the world when it was built in the 1880s, this one runs underneath Williamsburg, Brooklyn.

13

Salle Egyptienne, Paris Catacombs

Perhaps the most beautiful of all the cataphile-decorated spaces in the underground complex.

14

Old Croton Aqueduct, NYC

New York's first water supply tunnel, now unused except by the roots of many trees.

15

Tyburn River sewer, London

The Tyburn River was an important waterway from the beginning of London's history, originally flowing into the Thames by Westminster Chapel.

16

Utility tunnels, St. Paul, MN

An incredible labyrinth of tunnels extends underneath St. Paul.

17

Park River, Hartford, CT

The Park River is the largest urban underground river I've been in, and the only one I've been able to canoe through.

18

Roosevelt Island smallpox hospital, NYC

The view from the abandoned smallpox hospital on Roosevelt Island in New York.

19

Sewer, Rome

Rome's sewer system still includes sections of the old Cloaca Maxima from the days of ancient Rome, a sewer now more than 2,000 years old.

20

Tibbetts Brook, Bronx, NYC

The old Tibbetts Brook, now running underground in the Bronx.