Tunnels

These purpose-built WWII air raid shelters, which run half a kilometer under the town of Mellieħa, are among the longest in Malta.

Over 80 years old, this hand-dug tunnel is a Chinese-style portal to another world.

A Japanese-era military tunnel is now a psychedelic art exhibit.

View Japan's most historic city from a cyberpunk walkway suspended 150 feet above the ground.

These secretive tunnels were once the site of a Royal Air Force fuel reserve depot.

A 1,000-foot-long railroad tunnel under Shavers Fork connected the towns during West Virginia's logging boom until its closure in 1985.

A vertical tube that allows you to see what's going on underneath the Antarctic sea ice.

Nature has shaped this drainage tunnel into the digestive tract of a mighty beast.

The San Marino-Rimini railroad was short-lived but this tunnel once provided shelter for hundreds of refugees during World War II.

Nicknamed the 'Chestergate Hotel,' the underground tunnel had beds, lights, and even flushing toilets.

Cross the Continental Divide through an old railroad tunnel, and ride back to the top on a shuttle.

An underground passage is home to a guillotine that predates the French Revolution by more than two centuries.

Once a passageway that led to the Shaniwar Wada palace fort.

A dedication plaque on this Boston tunnel is a microcosm of a massive, controversy-laden construction project.

This colossal underground passage paved the way for large-scale drainage and access tunnels across the U.S., but it almost wasn’t built.

A network of ancient tunnels and vaulted chambers with mystical Buddhist reliefs, built for ascetic training.