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

A German apartment building hosting as many trees as human occupants.

A naturally mummified 2,000-year-old man.

A village on the east coast of England that has almost completely eroded into the North Sea.

A sign at the end of the Santa Monica Pier marks the traditional end of the legendary American highway.

A lone cannonball remains lodged in the walls of the Hotel de Sens as a sober reminder of a revolution.

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.

Designed by Buckminster Fuller, this relic of the 67 Expo survived fire and ice.

Abstract dinosaur models in London.

Fascinating town where normal life interfaces with the occult.

The prototype for all Nazi concentration camps.

Three columns of volcanic rock shoot out of the ocean.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

A miniature Italianate fantasy village on the coast of Wales and the set of ITC classic "The Prisoner."

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

The oldest operating pharmacy in the world features 800-year-old recipes.

The John Snow Memorial marks the epicenter of London's 1854 cholera epidemic.

A wall of chewing gum moonlights as collective art.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

Dictionary Johnson’s favorite feline.

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

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

A stratovolcano located in the south of Iceland, with a long history of charted activity and a rich mythology attached.

This expansive bridge in the Canadian wilderness was originally just built for friends.