The walls of this medieval church are covered with perfectly preserved frescos, including a pristine example of the Dance of Death.

This abandoned Slovenian military barracks has become a punky-political art squat.

A whimsical bridge adorned with decorative dragons.

A miniature train-ride through Slovenia's largest cave system.

This one-time health resort was used by aristocrats around the world.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

This massive subterranean fissure is known as the "underground Grand Canyon."

The abandoned "Ghost Mansion" was left to decay in the mountains of Northern Italy.

Iron Age runes and ruins hide in plain sight along this Portuguese beach.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

The names Lúthien and Beren can be found inscribed on the shared grave of the famous writer and his beloved wife and muse.

A reconstructed farm shows what life was like in Norway 1,500 years ago.

Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

A line of abandoned, alien-like fortresses dot the mountains of North Italy.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

A historic London cemetery now serves as a nature park incorporating gravestones & memorial statues.

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

One part local history, 99 parts gruesome haunted house.

A former top secret nuclear fallout shelter now operates like a hotel stuck in the Cold War.

America's post-nuclear-attack chambers of Congress.

This 1,300-year-old marker is one of the finest and most complete early Christian crosses in Scotland.

The atmospheric road was never meant to be so creepy.

See wolves, coyotes, and arctic foxes in a natural environment smack in the middle of New York State.

A little-visited waterfall in an otherworldly landscape.