The Church of the Annunciation was carved into the face of a cliff, just like the rest of the town of Haute-Isle.

Abandoned railway line circling the city of Paris.

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

A museum of carnival attractions where you are invited to ride the rides.

The industrial architecture honors the laborers who brought the Exposition Universelle of 1900 to life.

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

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

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

A model train wonderland hidden beneath Gare de l'Est station.

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

This recessed garden protects thousands of mountain plants by creating its own microclimates.

The history of radiation is on safe display at the foot of a radiation science laboratory.

The remains of the medieval wall that once surrounded Paris with ties to the construction of the Louvre.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

Architect Le Corbusier built his friend a cubist house to match his impressive collection of cubist art.

Experience architect Le Corbusier's modernist design for living in the home he designed for himself.

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

This Parisian gem is one of the most incredible ethnographic museums in the world.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

A tongue-in-cheek arcade where the games are based on everyday life.

A cluttered and astounding collection of antiquities and curiosities.

This coffee shop lies hidden beneath a historic church.

A living memorial to the trees London lost during the Great Storm of 1987.

Victorian-era Londoners really wanted to believe this 17th-century cistern was actually an ancient artifact.