Yale University's home for rare works, including the mysterious Voynich Manuscript.

A gargantuan crystal kingdom.

Once the home of a hermetic monk, this cave now houses a small church.

Limestone grottoes turns everyday objects into stone.

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.

The world of the ancient Celtic civilization explained through a bewitching 11 acre garden.

A tiled, multi-level garden of survival in Lyon.

Hundreds of hidden passageways weave through the old quarters of Lyon.

For hundreds of years, automatons moving to metallic music have been marking the passage of time.

An architectural oddity of six stories, accessed by graceful ramps.

Hungarian self-built castle.

Synagogue built from the stones of Solomon's temple contains the golem of Prague.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Macabre astrological automaton clock dating to the late 1400s.