A modern-day Lascaux cave underneath Paris.

Two awe-inspiring globes from the reign of the Sun King hang from the ceiling of France's national library.

This surreal statue brings a famous French novel about a supernatural cad to arresting life.

An all-American grocery store in Paris sells U.S. "cuisine" like Pop-Tarts and Heinz ketchup to homesick ex-pats.

This Parisian café sticks almost exclusively to an ethos of reuse.

An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

The largest medical and anatomical collection in France lies hidden from the public.

A scenic canyon with thick forests and historic ruins.

The odd depiction of the Virgin Mary and baby Jesus is rooted in the Catholic Church's eradication of Catharism.

This architectural beauty is the home to a personal collection of more than 600 examples of mechanical musical instruments.

This charming railway is one of the oldest and steepest funiculars in England.

Folklore says this medieval fortress was plopped atop a portal to hell to trap the demons below.

This huge abandoned fortress hidden inside a mountain holds a world of subterranean secrets.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

This cavernous abandoned marble mine is popular with ice skaters in the winter.

A beautiful South Korean gate and garden in Little Rock honors American Taekwondo.

At just 25 inches at its narrowest point, it's one of the tightest streets in the world.

Affectionately known as "Lord Bot," this historic statue has a cult social media following and rightly claims to be “the most metal inhabitant of the Wren Yard.”

Arthur, Merlin, and Guinevere are among the largest and oldest satellite dishes on the planet.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

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

The ceiling of Prohodna Cave in northern Bulgaria affords a peek at the sky via two deity-sized-eye-shaped holes.

The cedar tree in Highgate Cemetery earned its title by accident.

The first attack on the continental U.S. during WWII occurred off the coast of a quiet California golf course.