A natural arch carved by a river gave its name to the so-called "Cave of Forgotten Dreams."

A French library that makes sure its love of books is writ large... giant in fact.

A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

Large Hadron Collider and the Birthplace of World Wide Web.

One of the greatest maze designer’s greatest mazes.

Hundreds of hidden passageways weave through the old quarters of Lyon.

A tiled, multi-level garden of survival in Lyon.

For hundreds of years, automatons moving to metallic music have been marking the passage of time.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

France's Lilliputian park displays over 100 of the country's monuments for visitor perusal.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

Massive puppet-automaton machines created by French artist collective Machines de l’Ile.

An iconic and eccentric bar for "Manouche" Jazz music keeps expanding its space—and its influence.

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

This museum houses an imposing skeleton army comprised of creatures great and small.

A haunting collection of the vanished and disappearing natural world.

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

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

France's national museum of scientific and industrial instruments.

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

In this historic region, homes and churches are carved into ancient volcanic rock formations.

This WWII-era military installation once held an entire city within its walls - now, its walls are falling down.

Live out your childhood construction fantasies in this one-of-a-kind gyrating hotel.

Nikola Tesla's ashes are held in a golden sphere, surrounded by his works.