Subterranean Sites

A spectacular Bulgarian cave resembling a devil's head with a waterfall rushing down its throat.

This eccentric cave dwelling is bizarre even by the standards of a subterranean town.

Go deep down into the earth to experience the world of Welsh coal miners.

One of the most remarkable caves in all of Iceland was created by a once raging river of lava.

This submersible road connecting a French island to the mainland is lined with safety towers for when the tide strands travelers.

This narrow path was cut right into a French mountainside to feed the country's early naval expansion.

One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.

A museum dedicated to a secret military hospital hidden beneath a castle in Budapest.

Once the path of a railway tunnel, now home to thousands of glowing insects.

A subterranean Holocaust refuge within one of the world's longest cave systems.

Decommissioned NYC subway cars are dumped into the ocean to create this underwater wildlife habitat.

It should come as no surprise that the best view of the Hollywood sign is from Batman's lair.

An underground city of ancient quarry tunnels hid thousands of Allied soldiers in WWI.

Underneath a chalk hill in France lies what Hitler hoped would be the underground launching base for a devastating new weapon.

A former copper mine which became a truly unsuccessful prison.

An open-air sewer system that was covered piece-by-piece over 300 years.

This museum preserves the hand-dug tunnel that kept Sarajevo afloat during the Serbian siege.

Semi-precious Blue John stones have been mined in this cavern system for centuries.