Dating back almost 400 years, the oldest public collection library in the United Kingdom was once the study hall of Karl Marx.

A Victorian Gothic masterpiece housing a world-class collection of rare books and manuscripts.

Be on the lookout for the symbolic insect all over the city.

Have a seat with the father of modern computing at this Manchester monument.

A 400-year-old church covered floor to ceiling in ex-voto offerings from the faithful.

France's national museum of scientific and industrial instruments.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

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

The world's largest historic armory was established by independent citizens to defend themselves from the wars of larger forces.

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

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

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

The iconic castle that withstood a magnitude 6.2 earthquake has become a symbol of resilience.

These Japanese ruins have been brought back to life with elaborately recreated buildings.

The university library shaped like a giant piece of Swiss cheese.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

This massive fiberglass Gulliver turns every visitor into a Lilliputian.

Model Trains and Much More in Hamburg.

The Goose Girl of Göttingen, Germany might well be the most kissed girl in the world.

A sprawling Baroque park with 300-year-old hydro-pneumatic waterworks.

Four-story slides send people whizzing through the math department at this Munich university.

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