An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A brightly colored natural bridge formed by mineral-rich hot springs high up in the Andes.

A toxic lake near a volcanic caldera that is home to flamingos and other life.

The inspiration for the Patagonia Clothing logo, Cerro Fitz Roy turns pink at sunrise.

This stunning mass of ice spans 121 square miles and is still growing.

"Di amigo y entra" at this Argentinian Middle Earth-inspired pub.

Blue-green pools and smooth stones comprise one of Spain’s most idyllic hidden wonders.

One of the most spectacular bridges in Spain spans a narrow chasm that divides the city of Ronda.

Its appearance in "Game of Thrones" may spur on the long-awaited restoration of this medieval shipyard.

A charming Spanish village sits atop this natural limestone overpass.

The chefs at El Diablo use heat generated by an active volcano to cook the food.

A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.

This awesome Spanish castle is so fantastical it was actually used on Game of Thrones.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

An enchanting monastery in the Spanish countryside appears lifted from a fantasy tale.

A beautiful but toxic fountain of mercury.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

This semi-secret storybook hedge maze is also the oldest garden in the city.