Abandoned railway line circling the city of Paris.

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

Ancient paintings known as the "Sistine Chapel of Cave Art."

One of the greatest maze designer’s greatest mazes.

The first green space constructed on an elevated viaduct.

An icy lake tucked among jaw-dropping alpine panoramas.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

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

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

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

This natural French spring has been turned into a magical grotto by Roman and medieval constructions.

Two small chapels housed inside an ancient tree.

A beautiful and classically designed villa, with an hourly infestation of monsters.

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

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

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

An aluminum skeleton brings Chinese mythology to the French shore.

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

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

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

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

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

Lyon, France is home to two remarkably preserved Roman theaters, one dating back to 15 BCE.

This ancient Roman bridge and aqueduct still stands as a wonder of classical construction.