A hidden treasure in London with a rich medieval history, and the resting place of many luminaries.

This logic-defying 16th-century Tudor manor still stands to the delight and astonishment of onlookers.

Walk through living pictures and music in the Cathedral of Images.

This former limestone quarry is now a subterranean wonderland of grand stonework.

The world's largest drain sits below the city of Kasukabe, Japan.

This cavernous swimming spot doubles as a home to the largest known colony of bats in Central Asia.

Abandoned medieval hill town.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

Terrifying derelict military hospital once housed a recuperating Hitler.

Once the most densely populated place in the world, this island is now a ghost town.

A formerly opulent Italian village is now a crumbling ghost town that no one really knows what to do with.

Hidden beneath the streets of London is a secret subway that only carried mail.

Where Aleister Crowley taught magick in "La Chambre Des Cauchemars," his "Chamber of Nightmares."

An eerie, derelict amusement park in Berlin.

A fiery crater has been burning in the Karakum Desert since 1971.

An enormous, 30-story-deep hole in the middle of Guatemala City.

This Detroit ruin was once a gothic bastion of its community, but now it stands as a haunting ruin.

This abandoned Poconos resort is haunted by a history of kitschy romance and a violent fugitive.

Hidden in a secluded Greek cove is a pristine beach marred only by the rusting smuggler's hulk stranded on its shores.

Rusting ships sit in a desert where a sea used to be.

Below a historic English market town lies a secret underground city complete with kitchens, laundries, storerooms, and an underground lake.

This old Estonian mine has been kept like a sprawling time capsule of the local shale industry.

The world's second-largest excavated hole.

Naturally formed rock city in Poland.