Underwater art project will double as a massive artificial coral reef to help regenerate the damaged ecosystem.

A crumbling island fortress that seems to be covered in a field of stone crosses but is simply incomplete.

A small town hallucinates en masse - Bad bread, or CIA science project?

Longest canal tunnel in the world, abandoned in the 1960s.

Artist's eccentric property excessively decorated with found objects and work of his own.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

Personal garden filled with mosaics made of recycled garbage.

His "Lionheart" is entombed separately from the rest of his body.

The man who introduced reinforced concrete to the world demonstrated its genius by using it to build his own house.

In this Parisian garden's grotesque former life as a zoo it fed exotic animals to the bourgeois and put humans on exhibit.

To the famous surrealist artist, liberty required two torches held high.

Dedicated to the history and culture of smoking, this small museum now includes a vape lounge.

One man's desire to transcend art led to the construction of this outsider chapel.

One architect's organic, human-centric design has been fully realized in this alien art house.

One of the largest ochre quarries in the world, hidden in a limestone landscape.

Artist Danielle Jacqui decorates nearly every inch of her home inside and out with her work.

The construction of a tram line unveiled hidden remnants of the old medieval city.

A village of art and exotic creations.

An unsettling shrine dedicated to the ravenous beast that prowled 18th-century France.

A magical, macabre wax museum, beloved by locals, uses real artifacts to depict an assassination from the French Revolution.

The mummified heart of Louis XVII, the lost dauphin of the French Revolution.

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

Jean Tinguely's bizarre monster sculpture is hidden deep in a forest.

One of the world's most complex timepieces.