Completed in 2000, Norway's fifteen-mile-long Lærdal Tunnel cuts through a mountain range near the village of Lærdalsøyri. To ease drivers' claustrophobia and to prevent the underground monotony from lulling motorists to sleep, the tunnel is punctuated with a series of caverns designed to resemble impending daylight —…

Civil engineer William Lyttle was known as the "Mole Man of Hackney" after spending 40 years digging a network tunnels beneath his home. Now Lyttle's property is up for sale, although with considerably fewer tunnels.

Design writer Alissa Walker recently took a tour of L.A.'s original subway system, one whose tunnels are no longer in operation, though they remain down there bricked off and all but forgotten beneath buildings downtown.

The damp, dingy tunnels below Waterloo station in London are hardly your typical concert hall. But last weekend, as part of the Mindful exhibition, artist Oliver Beer brought a choir down to create ethereal music by turning the space into a giant musical instrument. To make the space resound, the singers needed to tap…

Singapore has embarked upon the excavation of an underground oil reserve, expanding the city's industrial port beneath the floor of the Pacific Ocean. It is "no ordinary construction site," the BBC tells us, but an elaborate project of engineering and infrastructure currently underway "several hundred feet underground,…

Churchyards and private farmlands throughout the German state of Bavaria are perforated from below by "more than 700 curious tunnel networks" whose "purpose remains a mystery."

70 or so feet underneath London's streets lies the unused mail rail system, a hard to reach subterranean system of postal tracks, cloistered away from human eyes. That is, until a gang of intrepid urban explorers cracked a secret entrance.

Urban explorers from Undercity took their cameras down below and into NYC's century old sewer systems, abandoned subway stations, and inside the Lincoln Tunnel to see the remnants of the society of tunnel folk. Watch what they uncovered.

The subway doesn't run 24 hours in Paris, but urban exploring in the Métro is nonetheless hazardous. Luckily for us, a group of intrepid urban explorers braved the City of Light's subterranean side and came back with awesome photos.

For much of the 20th century, New York's "Freedom Tunnel" was an unused rail tunnel that housed a homeless community and the occasional graffiti tagger. Trains run through the tunnel nowadays, but metro-spelunkers still venture down into this underground cathedral.