Martin Bricelj Baraga's monolithic sculpture measures the blueness of the sky, and changes color to match it.

A whimsical bridge adorned with decorative dragons.

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

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."

A hidden workshop for creating and restoring Papal mosaic masterpieces.

The Vatican's secret porn-festooned bathroom was painted in erotic murals by one of the greatest artists of the Renaissance.

Breathtaking and huge 430 year old maps of Italy.

If you want to talk to the Pope you will have to stare down this surreal vision of Jesus rising from a nuclear hell.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

One of Belgium's oldest hospitals saw patients from the 13th to 20th centuries before becoming a museum.

This collection of lurid religious statues tell the tales of a saint who stood down the devil.

The Belgian royal family's private depot now stands abandoned and forgotten alongside the tracks.

A moving memorial to the fallen and missing from WWI trenches.

A once-magnificent collegiate church is falling into ruin.

A Cold War command center is hidden under an idyllic countryside.

This modern arts center is built around a gem of late-Baroque architecture.

A Museum of Psychiatry in a still-operating mental institution.

Christ's blood allegedly preserved in a Belgian town.

A 14th-century fortified keep showcases the masterpieces of an ingenious 20th-century clockmaker.

Meet the bronze beloved pet to a family of famous peeing statues.

Theme park featuring miniature replicas of European monuments.

One of the deepest indoor swimming pools in the world.

Medical history with an amazing, if frighting, collection of wax diseases on display.