Croatia's towering concrete blossom grows from the site of a World War II concentration camp.

Longest fortress system anywhere in Europe.

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.

Humble beginnings for one of the world's most famous scientists.

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

Legend has it fairies gathered at the site of this medieval castle.

The complex has been abandoned since the Croatian War of Independence, barring a stint as a set for 'Game of Thrones.'

This huge metal monument is slowly being stripped to its concrete skeleton.

The remains of a sunken military ship wreck visible through clear water.

Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

A wonderfully strange collection of 500+ stuffed frogs doing people things.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

A musical instrument played by the sea.

An ethereal glowing blue ocean cave in Croatia.

The oldest private art gallery in all of Hungary.

This quiet, unassuming spot in Budapest was the birthplace of the bloody 1956 Hungarian Revolution.

A beautiful display of nearly 50 bells crafted with a unique design and distinct sound.

A two-way chairlift system between Zugliget and the highest point in the city.

Hundreds of boat-shaped headstones fill this graveyard as part of a centuries-old custom with mysterious origins.

300 years of pharmaceutical history on display.

The geographical center of Budapest is marked with a 10-foot-tall stylized zero.

The massive white mound and accompanying water terraces are a striking geological oddity.

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