The largest cave chamber in Britain—big enough to fit a whole cathedral inside.

This medieval sanctuary's tree-framed door looks like a portal to a mythical realm.

Created hundreds of years ago, the magical follies and landscapes at this park were almost lost to time before being restored.

A pagan tradition of draping trees with rags eerily lives on.

English antique dealers with a taste for the unusual.

Once thought to be the mysterious work of a witchy prophetess, a well with unusual properties turns objects into "stone".

A unrivaled and rather horrifying collection of wax dermatological models.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

A grotto-like lodge decorated with gilded mosaics, rocks and a noisy waterfall was the setting for the most sumptuous pleasure house of 1900s Europe.

Stroll through retro Paris while shopping for old postcards and discarded doll heads.

Paris' fabled purveyor of exotic taxidermy and natural history curios.

This Parisian fountain is a little bit fantasy and a little bit nightclub.

This small museum in a former church crypt contains artifacts of the Elephant Man, Jack the Ripper and Florence Nightingale.

This hidden green space is the city's second largest conservatory.

Egyptian Revival movie palace abandoned for decades and restored in 2013.

"In the Dark" Restaurant in Paris offers dinner in complete darkness.

Japanese island famous for poison gas and fluffy bunnies.

The elaborate clockwork contraptions in this Scottish gallery create small worlds of whimsy and horror.

A subterranean playground in an abandoned slate mine.

A collection dedicated to the treatment of disease, held in London's oldest hospital.

Mysteriously stacked storefront paths give this medieval British town an iconic style like none other.

One of the world's largest collections of pathological specimens.

A church that bred legends, and served as an inspiration for the Da Vinci Code.

The largest of London's subterranean rivers and once a mad, bad center of London life.