Austria's ultra-modern art museum looks like Cthulhu's giant alien heart.

The housing complex served as an anti-fascist fortress during the Austrian Civil War.

The world's oldest known salt mine.

Resting in the middle of an Austrian river, this sci-fi "island" lets people cross in neon style.

This series of underground chambers contains Europe's largest subterranean lake that is slowly drained each day.

This series of Baroque passageways in Vienna's cultural center mix old architecture with modern art.

The solemn exterior conceals an opulent interior of this 17th century church.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

A neo-Gothic church built to thank God for saving the Emperor of Austria from an assassination.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

Legends surround an ancient tree trunk riddled with nails for good luck.

Baroque celebration of the end of the Great Plague of Vienna.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

Op-art architecture designed for happiness.

The topiary maze at the Habsburg hunting lodge.

Once the fallout shelter of a dictator, this sprawling bunker is now a combined history museum and contemporary art gallery.

What happens when you cross a mayor and a painter?

Hundreds of thousands of concrete bunkers crowd Albania long after the fall of Communism.

During the Soviet era, the spire of this longstanding church was used as a radio transmission tower.

A spectacular Petrine Baroque summer palace commissioned for Catherine I by Peter the Great.

This abandoned fighter jet launch center is now a haunting street racing course.

This dizzying tower was built to better broadcast the 1980 Moscow Olympics.

The oldest continuously operating pharmacy in Europe.

Disused seaplane hangar gets a second life as the jaw-dropping home of Estonia's museum of maritime history.