Romania's "Red Ravine" is a little-known natural wonder that bears a resemblance to the Grand Canyon.

No one knows who built this strange cave of worship or exactly why.

This once-derelict building is now one of the most beautiful bookstores in the world.

The legendary cliffside castle of three-time Voivode of Wallachia, Vlad the Impaler.

The romantic botanic tunnel feels like a well-kept secret.

Some call this eerie forest of crooked trees the "Bermuda Triangle of Romania."

This massive underground salt mine now holds a sci-fi theme park in its depths.

Moss and stone turn this waterfall into an otherworldly liquid veil.

It's said the devil used this mushroom rock as a table for a late-night meal.

This frog-themed restaurant was frequented by Picasso, Saint-Exupéry, and more.

In this Parisian garden's grotesque former life as a zoo it fed exotic animals to the bourgeois and put humans on exhibit.

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

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

A subterranean shelter remains intact under a busy Paris railway station.

Behind the pink curtain, Au Bonheur du Jour, an art gallery of erotic archives.

This massive library holds what was once the largest book collection in the world.

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

Notorious artist squat renovated into legal studios.

Abandoned railway line circling the city of Paris.

France's most famous cemetery, with some of its most curious tombs.

This contentious squat has stood through fire, violence, and government intervention as a hotbed of leftist protest.

A fascinating little museum dedicated to the thousands of chemical substances concealed in our food.

Hamburgers are intensely proud of their tunnel beneath the river.

Remnants of an exploded schooner and wrecked submarines form a breakwater.