This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

Amsterdam's former hotspot for public executions and dissections.

Cat art as far as the eye can see.

Old ships and machinery fill a historic harbor in the city that's home to Europe's largest port.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

A dramatic art installation features a BMW flying out of a building in Rotterdam.

These slanted cubic abodes are a creative if odd solution to a zoning pickle.

This charming pup is meant to celebrate the youth and stubbornness of the city's students.

A nearly 25-foot concrete sculpture of Sylvette, Picasso's muse.

Rotterdammers' dirty minds gave this santa a dirty nickname and cursed it to a life of wandering.

A statue of the second-tallest Dutchman in history.

A floating cat sanctuary on an Amsterdam canal.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

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

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

Famed for its pie, this eatery has a hidden tunnel that allowed Catholics to secretly walk to church during the Reformation.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

Incredible labyrinth of man made caves.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

Naturally formed white marble arch housed in an abandoned marble quarry from the 1800s.