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

This beautiful Croatian fortress is haunted by legends of forbidden love.

The only gulag ever to exist in socialist Yugoslavia.

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

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

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

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.

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

Yugoslavia's biggest underground airport lies in ruins.

An ethereal glowing blue ocean cave in Croatia.

Swarovski's museum/theme park is a fake diamond fantasia overlooked by a giant.

A breathtaking viewing platform over the Alps.

American soldiers discovered Europe's best one-liner at the end of World War II.

The world's oldest known salt mine.

The largest ice cave in the world is thought to be the entrance to hell according to Austrian legend.

Walk inside a half mile long crevice right outside the town of Garmisch Partenkirchen.

Part ski resort, part modern art space, this lodge brings giant metal spiders and bloody doors to the Austrian Alps.

Things aren't quite what they seem at this mind-bending museum.

Once known throughout Europe, this tiny and unusually progressive 18th century micro-nation within Lithuania now lies in ruins.

The charmingly disheveled clock tower of Tbilisi's puppet theater.

A trio of giant wooden megaphones turn up nature's volume in this Estonian forest.

An art museum inside an active factory.

A surreal pile of colorful junk fills a small yard in an otherwise gray neighborhood.