An eerie, derelict amusement park in Berlin.

Go inside to really appreciate this 500-year-old technological masterpiece.

As can be expected from a centuries old church built in a canal city, the undercroft of this house of worship is beautifully flooded.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

This community on a small Venetian island has taken to painting their houses in bright neon hues.

This massive subterranean fissure is known as the "underground Grand Canyon."

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

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

A whimsical bridge adorned with decorative dragons.

This abandoned Slovenian military barracks has become a punky-political art squat.

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

Where the lovelorn find a home for their sentimental keepsakes.

This former estate of a fascist leader is now a burnt out ruin leading to a system of secret tunnels.

This scale model of our solar system hid in plain sight for years before a physics team sought out all the planets.

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

One of the largest barracks of the Austro-Hungarian monarchy's military is now an abandoned ruin.

The remains of an entire Roman city can be explored in this interactive museum.

Hungarian self-built castle.

This hidden art nouveau gem was designed by an architect in search of a national style.

Possibly the world's largest hourglass only needs to be reset every New Year's Eve.

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

Sitting beneath an unremarkable residential building is a museum devoted to classic Pinball.

This off-beat, quirky communism-themed bar isn't afraid to poke fun at its history.

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.