Tunnels

Following years of secrecy, the hidden history of a World War II site is being brought to light.

This gaping hole in the middle of a remote mountain lake looks like a portal to another dimension.

A subterranean world of tunnels links several buildings of this rare 19th-century asylum.

This centuries-old mine remained hidden beneath a hotel bar until 2013.

These underground shelters dug by the Japanese during World War II later helped Timor-Leste achieve its independence.

Not far from Madrid, a set of perfectly preserved trenches date back to the Spanish Civil War.

These crevices cut into the mountains collect the island’s main source of precious freshwater.

This secluded walking trail is a hidden gem of a Pittsburgh park.

This army of concretions is an unexplained geological phenomenon unlike anything else in the world.

Built on a medieval synagogue, this church has a burial crypt, tunnel system, and Jewish ritual bath hiding deep underneath.

An enchanting tunnel of cypress trees leads to an old morse code station still used today.

The railway carts travelers to central Athens's highest peak, which offers stunning vistas of the city.

A network of concealed passageways lies within a busy London Underground station.

There's a labyrinth of manmade tunnels stretching for over an acre beneath Bristol.

The fishing boats that moor in this small lagoon enter and leave through a tunnel to the sea.

The abandoned funicular tunnel was a secret base for the BBC during World War II.