This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

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

One of the highest emergency huts in the world has been waiting almost a century to give imperiled climbers a place to lie down.

This ancient theater was once the home of fierce gladiatorial battles.

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

These quaint French houses dangle precariously over a precipice.

The mental institution where Van Gogh created some of his most famous work now allows guests to walk in the artist's footsteps.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

One of the greatest maze designer’s greatest mazes.

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

In one of the world's smallest countries, a royal's personal winery is open to the public.

Paris' linguistic guide to the international language of, yes, love.

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

Abandoned railway line circling the city of Paris.

A breathtaking flower tunnel bursts with beautiful golden blossoms.

This abandoned asylum in Wales might look haunted, but it's still beautiful.

A rocky sea serpent hides caves, blowholes, and a spectacular natural bridge.

This lonely cast-iron structure is the only wave-washed lighthouse of its kind left in all of Britain.

Abandoned ship reimagined as a street art canvas.

A hidden tunnel leads to an abandoned slate quarry that's now a secret swimming spot guarded by cliffs.

This 19th-century island fort built to protect against an invasion by sea.