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

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

A medieval military street hidden beneath a charming French fishing village.

Avant garde house of Pierre Cardin on the Cote d’Azur.

Monsters and miniatures are held in equal esteem at this wondrous museum.

An aluminum skeleton brings Chinese mythology to the French shore.

This is what trains will look like after the zombie apocalypse.

These quaint French houses dangle precariously over a precipice.

A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

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

The headless bodies of more than 1,300 guillotined victims of the Reign of Terror are buried here in mass graves.

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

This Paris art space celebrates the creativity and ingenuity that springs from abject poverty, especially in Africa.

The recovered bones of martyrs slaughtered during The Terror are on display in this church crypt.

The famous winding walk at Chartres is surrounded in mystery and myth.

This museum in a Paris apartment gives a unique look at the iconic French singer's life.

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

This massive blockhead sculpture hides an entire library.

This banal Parisian entranceway is not what it seems.

This off-limits room in the National Library of France is home to a system of pneumatic tubes, once used to bring books to readers.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

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

A lone cannonball remains lodged in the walls of the Hotel de Sens as a sober reminder of a revolution.

The largest underground church in Europe.