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

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

Double spiral staircases are not unheard of, but they are very rare.

Op-art architecture designed for happiness.

Each year melting snow turns these Austrian hiking trails into scuba zones.

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

The 20-mile causeway that separates the Netherlands from the sea.

Amsterdam's former hotspot for public executions and dissections.

Rich with fauna and flora, nature-lovers can walk across the sea at this UNESCO World Heritage spot.

A miniature city, once ruled by the Queen of the Netherlands.

A little sculpture with a large wardrobe.

Climb inside an iron crystal magnified 165 billion times its normal size.

18th century opera in its original splendor.

This striking royal residence is the largest Renaissance-style castle in Scandinavia.

A distinctive former power plant turned university lecture hall looks like it could make you breakfast.

The skeletal frame of a decommissioned gas-pumping station offers breathtaking views of greater Berlin.

This historic toy museum brings a little whimsy to a city not usually remembered for such things.

Take a walk in a recreation of ancient Rome.

Böttcherstraße's bells, extolling Nordic virtues and the great conquerors of the world.

Tiny castle in the middle of the Rhine made you pay to pass.

A memorial for a young woman and her ghost, which are claimed to have caused countless deathly shipwrecks.

The small alleys in Lübeck's Old Town are a result of medieval urban sprawl.

Legendary site where an evil bishop was devoured by rodents.

Sitting in the basement of a castle, the largest wine barrel in the world is bigger than most apartments.