Ivy-covered Medieval tunnels cut through this charming town in France's Loire Valley.

The world's largest reflecting pool is just two centimeters deep.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

A public park off the beaten path with a beautiful waterfall and 13th century Cistercian abbey.

Two small chapels housed inside an ancient tree.

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

This professional clown's home is an outsider art wonderland.

These quaint French houses dangle precariously over a precipice.

A French valley with forests so lush it was nicknamed "the Small Amazonia of the Pyrenees."

An aluminum skeleton brings Chinese mythology to the French shore.

This stunning natural double arch, the largest in the Alps, went undiscovered until 2005.

Do these monsters look familiar? The gargoyles on this church are all from pop culture.

This banal Parisian entranceway is not what it seems.

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

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

A 14th century bridge built as a fortress, where the devil lurks on one of its towers.

An icy lake tucked among jaw-dropping alpine panoramas.

One of the greatest maze designer’s greatest mazes.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

This Parisian fountain is a little bit fantasy and a little bit nightclub.

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

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

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

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.