A tower marking the spot where Yugoslavia began its resistance against the invading Nazis stands neglected, but not quite forgotten.

Formerly Yugoslavia's "forbidden island," this sleepy little city still holds the abandoned remains of military strongholds.

When Croatia became independent of Yugoslavia, the splintering governments left behind these concrete tunnels.

A wunderkammer of gold and silver reliquaries and ancient saintly bones.

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.

Longest fortress system anywhere in Europe.

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

Gargoyle head that brings good luck.

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

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

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.

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

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

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

A musical instrument played by the sea.

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

An ethereal glowing blue ocean cave in Croatia.

This ancient burial mound is accessed by an impressive Greek-built archway.

In the land of the Light Brigade stands a testament to the Cold War.

Over 300 wood sculptures depicting characters from Slavic, Greek and Western folk tales fill this magical garden.

Submerged busts of communist and socialist figures from the USSR.

A castle perched precariously over the Crimean Sea.