Rusted structures stand like ghosts of Cyprus' 6,000-year-old copper industry.

This former Cyprus flight hub is now a crumbling, abandoned ghost complex.

This abandoned Croatian stronghold never saw a great deal of conflict but it is still a beloved relic nonetheless.

The now-overgrown beach resort was once frequented by Yugoslav military elite.

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

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

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.

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

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

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 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.

A gigantic statue of a Russian soldier watches over the ancient city of Plovdiv, a prominent reminder of the Soviet period in Bulgaria.

A magnificent, glittering building tucked into a tiny Bulgarian mountain town.

"Unity, Creativity, Beauty."

A striking symbol of the Bulgarian capital.

The second-largest Jewish temple in Bulgaria was deserted after World War II, seized by the communist government and then abandoned again.

The site of many battles and tragedies, including the 40 maidens who leapt into the sea.

The ceiling of Prohodna Cave in northern Bulgaria affords a peek at the sky via two deity-sized-eye-shaped holes.

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

This massive concrete sculpture is said to be the heaviest communist monument on Earth.