A repurposed railway tunnel with otherworldly acoustic characteristics.

These Bullet-scarred bunkers are haunting reminders of the Spanish Civil War.

Abandoned for decades, trains still pass through the now-restored remains of one of Madrid's first metro stations.

An arcade packed with a rotating collection of unique independent video games.

The hidden ruins of an old hydroelectric plant reclaimed by nature.

The tangled roots of a giant banyan tree have fully reclaimed the ruins of this abandoned warehouse.

The remains of an ancient Roman city are hidden underneath Bologna's beautiful public library.

On this stunning Scottish island, you can walk in the footsteps of dinosaurs.

This high-Andean reserve protects the graceful vicuña that was nearly hunted to extinction for its precious wool.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

One of Europe's largest supercomputers is housed inside of a disused chapel.

Bask in the 19th century grandeur of an eccentric Freemason millionaire's private gardens.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

One of the world's largest collections of medieval religious art.

A Christian monastery stands on what was once a holy Incan temple.

The sophisticated hydraulic system of the Nazca civilization.

An ancient city hidden in the heart of the Sierra Nevada mountains.

The world's tallest palm trees look like the whimsical kind of plant you'd find in a Dr. Seuss story.

A little known Colombian theme park of giant curiosities.

Colorful lights and mirror-like brine pools create trippy illusions within the historic mine.

Unparalleled stargazing, one of Colombia's best observatories, and a swimming pool can all be found in the middle of this ancient tropical forest.

The Andean town where every single building is decorated with a brightly colored frieze.

This picturesque mansion has gone from opulent ruin to nature museum.

An explosion of natural color known as "the river that ran away from paradise."