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

Unusual building appears to be haphazardly built from randomly piled bricks.

A towering spire in the fortress of Kalemegdan honors the victorious armies of Serbia during their struggles against the Ottoman Empire.

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

Where the lovelorn find a home for their sentimental keepsakes.

This one-time health resort was used by aristocrats around the world.

Martin Bricelj Baraga's monolithic sculpture measures the blueness of the sky, and changes color to match it.

This abandoned Slovenian military barracks has become a punky-political art squat.

The "dragon babies" of southeastern Europe.

A miniature train-ride through Slovenia's largest cave system.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

A whimsical bridge adorned with decorative dragons.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

Eat a meal surrounded by bomb fragments.

Believed to have once stored either human remains or rice wine, thousands of mysterious stone jars lie in ruin.

A small memorial to a deadly night in Serbia that shook the world before it was swept under the rug.

A pair of connected skyscrapers form this symbolic gateway.

This derelict superstructure was a very important warning system for the Soviet military.

This attraction was abandoned after the Chernobyl disaster.

The ghost town left by the worst nuclear disaster of all time is being taken over by nature and urban explorers.

An Art Nouveau building covered in animal gargoyles and grotesques.

One of the largest museums in Ukraine remembers the story of the German-Soviet War in iconic, brutalist style.

The deepest metro station in the world.