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

A former squatter's paradise outside Prague.

The last municipal pneumatic post system in the world was in operation for over 100 years, and may run again.

The deepest sinkhole in Central Europe comes with a grisly tale and an unusual nickname: “The Stepmother Abyss.”

Looming communist pillar with a Czech twist.

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

This former quarry is now a picturesque gorge that hides a sunken lake.

Bohemian paradise covered in majestic forests.

Thirty creepy ghosts now inhabit this decaying 14th-century church.

Street artists transformed an abandoned air vent into the beloved Star Wars robot.

Countless grotesque faces stare out from this eerie Prague art wall.

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

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

The majority of the highest mountain in Poland is actually located in a different country.

An open-air museum of 18th-century homes and churches transported from various villages in Southern Poland.

Come to this Polish museum to take a good, clean look at filth.

Dubbed "Wistom" by locals, this abandoned factory is an urban explorer's dream.

One of only two places in the world where two rivers cross each other without the waters mixing.

This fairytale medieval church in Poland originally spent centuries in Norway.

These massive moving sand dunes have swallowed an entire village and are still on the run.

Crosses of all shapes, sizes and colors litter the mountain, the site of a huge yearly Orthodox pilgrimage.

The world’s narrowest house makes for an awkward, four-foot-wide living space.

This man-made mound monument was built out of soil from all across the Polish empire.

Naturally formed rock city in Poland.