Most prolific publishing house in the 1600s open to the public.

Human-made caves excavated to hide a secret society of wealthy pagans.

The saddest little diner in New York.

Geometry and mystery come together in an epic show of octagonal masonry.

Shattered columns and Egyptian pyramids outside of Paris.

This natural gas vent certainly earns its name as the smallest volcano in Italy.

A community of artists and entrepreneurs seeks a simpler life on London's waterways.

"the sweltering inhabitants of Charleston and New Orleans, of Madras and Bombay and Calcutta, drink at my well . . . The pure Walden water is mingled with the sacred water of the Ganges."

A magnificent Victorian garden that brings the charm and style of old-time aristocracy to the 21st century public.

The Devil’s own choice when he needs a drink in Brussels.

A sulfuric hellscape in southern Italy.

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

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

A unrivaled and rather horrifying collection of wax dermatological models.

The largest underground church in Europe.

The seamy, underground secrets of Portland's criminal past.

Seventeen oak trees sprout from the roof and walls of this tiny chapel without any visual evidence of roots.

The longest hedge maze in the world.

The hermits of Karoulia protect their asocial lifestyles by living on the vertical face of a treacherous precipice.

Private collection of art inspired by cabinets of curiosity.

A former insane asylum despised by Nelly Bly and Charles Dickens is now fashionable apartments.

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

A fantastic castle rumored to be the birthplace of King Arthur.

The world's largest collection of witchcraft regalia.