A massive 1830s industrial site once known as Czechia's "Iron Heart" has been transformed into a playground of science, technology, and art.

These 17th-century mummies are no longer naturally preserved, but remain on display today.

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

Mysterious painted skulls in Moravia.

The world's greatest slide descends 18 stories from this looping mountaintop viewing platform.

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

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

Europe's second largest ossuary wasn't discovered until 2001.

This Croatian fairytale castle is slowly falling apart thanks to years of neglect.

Once a state-of-the-art tuberculosis treatment spa, these ruins are now ruled by paintball players.

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

This tiny Bulgarian town offers a stunning location in the mountains and a storied history.

This historic black and white monastery is one of Bulgaria's architectural jewels.

An architectural marvel that spans the Arda River, and has stories of a haunted past.

This historic cemetery was inaccessible for several years due to dozens of land mines.

The place where World War I began.

There's a mini version of Iguazu Falls hidden in the Balkans, and it's got a rope swing.

This museum preserves the hand-dug tunnel that kept Sarajevo afloat during the Serbian siege.

A war-torn Olympic relic is being overtaken by graffiti and nature.

This cluster of little wooden huts once ground local farmers’ wheat into flour during the days of the Austro-Hungarian Empire.

A wonderfully kitsch bookstore the size of a supermarket.

Each time a baby is born in Ghent, these streetlights flash in silent celebration.

A giant bug impaled on a 75-foot-tall needle.

This giant urban staircase was built to keep the city's brave fighting men from getting waylaid in the red light district.