This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

A collection of anatomical samples from one of the first anthropologists to suggest that humans reached North America by crossing the Bering Strait.

Two stunning 17th-century libraries and a cabinet of curiosities.

Walk through Czech history in Prague's largest graveyard.

A Jenga-style cylindrical tower of books that appears to go on forever.

Macabre astrological automaton clock dating to the late 1400s.

This Prague museum collects brutalist relics and memories from the country's former Soviet rule.

What looks like a crashed Zeppelin is actually a bright, airy reading room perched atop a modern museum.

A steampunk-styled three-floor factory churning out art, activism, and electronic beats.

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

One of the best-preserved Roman amphitheaters is still used today, but for less brutal events.

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

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

This truly palatial work of Communist-era architecture now sits crumbling on a Croatian beach.

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

Also known as the Blue Church, the building was consecrated to the daughter of Andrew II.

This spaceship sculpture in the middle of the Slovakian capital looks like it just crash-landed.

This series of underground chambers contains Europe's largest subterranean lake that is slowly drained each day.

This grand manse has been transformed into a museum devoted to one of the founders of Fantastic Realism.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

Located right outside of Vienna, visitors can take in expansive views of an ethereal forest.

The housing complex served as an anti-fascist fortress during the Austrian Civil War.

The largest medieval water tank on the Iberian Peninsula is preserved beneath the Cáceres Museum.