The fairy tale castle of the "fairy-tale king."

An underground city of salt.

Poland's oldest salt mine has nearly everything one needs to live underground forever.

A 20th-century picture show in 3-D.

An isolated dive site teeming with cnidarians.

Japanese company creates clone dolls that reside in the "uncanny valley."

Enormous underground chamber built to detect 'ghost particles' of the universe.

This attraction was abandoned after the Chernobyl disaster.

A serpentine highway twists and turns over the treacherous Norwegian Sea.

North Korea's massive "hotel of doom."

Secret North Korean passage discovered below the world's most dangerous border.

A geological bull's-eye visible from outer space.

World's only nuclear reactor operated by liberal arts undergraduates.

The largest underground church in Europe.

A breathtaking bridge that crosses a vast gorge over a river's torrents, and has a tale of a devil architect attached.

The original "capsule building" is a masterpiece of Metabolist architecture.

Enter the cabin of a life-sized Hindenburg replica.

From Ancient Rome to WWII, Neupfarrplatz has over 2,000 years of history underneath its main square.

A neutrino detector built into the largest man-made underground cavity in the world.

A sculpture park of the tossed aside relics of the USSR, from Stalin to a massive Soviet emblem.