Tunnels

This military tunnel dates back to World War II and provides visitors with a little wartime adrenaline.

This tunnel looks like a sliver of Shanghai that's stuck in the past.

The remains of a centuries-old water system that inspired local legends of secret tunnels.

It was meant to help transport wounded soldiers to a secret underground hospital.

This tiny 19th-century tunnel was built so a man could move his cows from one field to another.

It leads to a former hospital’s old root cellar.

A spooky defunct railroad tunnel now part of a sprawling trail.

A Victorian Fort built into the chalky cliffs that overlook the English Channel.

A repurposed railway tunnel with otherworldly acoustic characteristics.

This ancient tunnel is one of the most important examples of Roman hydraulic engineering in Spain.

This trail leads to a mine that was used as a sanctuary during the Great Fire of 1910.

The narrow passages will challenge even the bravest driver.

A labyrinthine underworld of tunnels and caverns hides beneath the city.

This recently restored crypt was once plagued by liquefying coffins and exploding caskets.

The site of one of the largest prison escapes of World War II.

The blowhole bursts spectacularly right next to the buildings in a medieval seaside town.

This old train trestle and collapsed tunnel once allowed the railroad to negotiate the steep slopes of the Colorado Rockies.