The atomic museum in the basement of this German castle displays long strands of replica uranium cubes.

A trio of red, white, and blue stones embedded in the streets of Leiden are markers of medieval territory and law.

The tallest waterfall in the Netherlands is a lovely, stepped feature that is only 50 feet tall.

The world's largest collection of mechanical puzzles is a cornucopia of analog bafflers.

This top-secret nuclear bunker hidden in a Bosnian mountain has been converted to a modern art exhibition space.

A fascinating insight into daily life in the Eastern Bloc.

This network of conjoined cellars was riddled with traps and supposedly allowed the townspeople to pretend their homes were deserted.

The secret cells in the basement of the KGB's Estonian "Grey House" have been preserved as a grim Cold War museum.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.

Once a strategically imperative naval base, portions of this Bermuda dock complex now serve cruise ships.

Take a stroll through the hellish grotesques of Hieronymus Bosch in this elaborate Netherlands church.

This Russian religious complex is a Frankenstein's chapel that includes influence from almost all the major faiths.

This replica Viking village was created for a film that was never shot and is now open to visitors.

This innocuous New Mexico storefront was once the secret jump-off spot for Manhattan Project scientists.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

Croatia's towering concrete blossom grows from the site of a World War II concentration camp.

The abandoned remains of this Victorian brewery hide crumbling bowling alleys and rusting industrial gear.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

This centuries-old Italian chapel hangs midway down a sheer cliffside.

The quaint little store that is said to have inspired a famous Dickens novel was only given its name after the book was released.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

This ancient abandoned church in a remote part of Turkey is in danger of falling over.

The world's first nuclear power plant is open to visitors looking to role-play a meltdown.

Discovered after draining a local pond, these ancient man-made caves are still a complete mystery.