The spiral staircase hidden inside this giant Parisian column was likely built for Catherine de Medici's astrologer.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

This little-known relic crypt holds stolen parts of a Roman Empress.

A popular shrine where the Blessed Virgin allegedly appeared in 1830, displaying a holy armchair and two incorruptible remains of Lady Saints.

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

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

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

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

A majestic lion statue guards this Parisian botanical garden, and feeds on an unsettling item.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

Stroll through retro Paris while shopping for old postcards and discarded doll heads.

A mechanized clock where a man fights off a dragon, crab, and rooster.

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

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

A haunting collection of the vanished and disappearing natural world.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

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

One of the oldest medical collections in Europe focusing on rare surgical instruments.

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

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

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

A crumbling bakery where forced laborers from the nearby concentration camp toiled to feed their fellow prisoners and Nazi soldiers.

In this brilliant blue spring in Germany, legend has it that a sad mermaid learned to finally laugh.

Albert Einstein's head sticks out of a snail shell stacked on a rocket in this truly bizarre monument to the scientist.