This abandoned airplane hanger is said to have once been a top secret launch facility.

These warring psychedelic crags commemorate an unsuccessful military operation.

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

This picturesque monastery at the base of a cliff is a peaceful oasis open to all visitors.

There's a mini version of Iguazu Falls hidden in the Balkans, and it's got a rope swing.

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

Longest fortress system anywhere in Europe.

A full figure 4th century incorruptible saint lies in a glass coffin in Croatia.

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

Inside this small chapel tucked away in the forest is one of the most well-preserved Danse Macabre frescos.

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

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

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

Yugoslavia's biggest underground airport lies in ruins.

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

Where the lovelorn find a home for their sentimental keepsakes.

The world's second largest single-dish radio telescope, once used to contact E.T.

Legend has it this historic port was a popular hideout and smuggling spot for pirates.

The abandoned remains of this once-thriving hotel looms over the city, awaiting an uncertain future.

This tiny home was originally a narrow alleyway.

An enchanting natural wonder in Puerto Rico's Camuy River Park.

The world's brightest bioluminescent bay.

This former sugarcane transport tunnel is now a portal to a lovely beach.

This small primate research island is teeming with playing, fighting wild monkeys.