This Nazi-built amphitheater was constructed on a sacred mountain site used by various German cults.

Abandoned Nazi train station turned underground astroparticle laboratory.

This sprawling Belgian fort was once thought of as impenetrable but now it is simply an abandoned relic.

This castle-fortress is a living example of the transition from medieval defenses to modern fortifications.

This 15th-century fortification was built to defend bunnies.

Henry VIII's forgotten castle was built by the gunpowder-obsessed king to be defended solely by cannons.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

The world's first purpose-built motor racetrack was destroyed by the outbreak of two world wars.

This striking fort on the Maginot Line looks just as it did after being destroyed in the Fall of France.

An abandoned World War II tank left to rust in the downland.

This Nazi ruin was the site where Hitler was almost blown up by a suitcase bomb.

A mysterious structure left behind on the Polish mountainside, sometimes called "Hitler's Stonehenge".

This open-air museum was originally a World War II testing ground for German missiles and rockets.

A massive, secret marina for the Nazis' most formidable weapon in the Atlantic.

Abandoned blockhouses from Nazi Germany's Atlantic Wall erode into the sea on a French beach.

Super-heavy Nazi architectural experiment.

Besieged by war, this castle ruin has crumbled into a peaceful picnic spot.

Largest lake in Great Britain measured by surface area.

A set of ancient drawings in the desert of Peru that are so massive, many of them can only be fully seen from the sky.

No need to strap in for a "ride" on this walkable roller coaster.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

Japanese gardens dedicated to the Japanese farmer that refused to throw in the trowel.

Not one, not two, but three natural bridges remain in this captivating spot post-sinkhole.

An oddities shop that dabbles in the deathly and beautiful.