Natural mummies hidden in the crypt of a medieval French church.

A Christian retreat founded to welcome refugees fleeing from the Nazis during World War II.

This French chateau is home to the world’s largest private collection of fighter jets.

This massive blockhead sculpture hides an entire library.

The construction of a tram line unveiled hidden remnants of the old medieval city.

An atmospheric, medieval-themed book store hides in a 13th-century underground space.

Foreign invaders almost left this lovely Caucasus palace alone—almost.

A village of art and exotic creations.

This stunning French estate was so lavish that it landed its original owner in jail for the rest of his life.

Peeing dogs guard the Roman hunting goddess atop a fountain at France’s Château de Fontainebleau.

A huge work of Burning Man-inspired outsider art on the grounds of a California winery.

Dedicated to the art of hunting, with juxtapositions of contemporary art.

This 170-year-old Swiss guesthouse built into the side of a mountain is best accessed by a cable car.

The oldest stone house in Paris was built by its most famous alchemist.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

Where the high court feasted, frolicked, and high courtesans put their royal lovers' diamonds to the test.

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

This extraordinary art museum is like a secret world on the edge of Mexico City.

This Parisian gem is one of the most incredible ethnographic museums in the world.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

A modern-day Lascaux cave underneath Paris.

An odd museum dedicated to French fakes.

Former hunting lodge of a duke who was an avid collector of impressionist works.