In the days before house numbers, these colorful signs held clues about various buildings' purposes.

Amsterdam's former hotspot for public executions and dissections.

A public urinal so pretty, it was declared a national monument.

A unique collection of gilded age mechanical pianos.

The world's oldest Jewish library was founded by Sephardic Jews in 17th century Amsterdam.

Seven mini rowhouses fill the gap between 54 and 70 Westerstraat.

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

A beautifully eclectic mix of architectural styles.

This marine reptile was discovered by one of the 19th century's greatest fossil hunters.

A statue marks the exact spot where The Boy Who Never Grows Up made his first literary appearance.

Eighty million natural history specimens call this gargantuan museum home.

Catacombs turned marketplace.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

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

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

The final resting place of the great navigator, or maybe his brother.

The effect of this ancient form of image projection situated atop an 11th century Moorish palace is thrilling.

A lavish 16th-century mansion filled with spectacular staircases, fantastic frescoes, and gorgeous gardens.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

A lonesome Moai stands in a small Italian town some 9,000 miles away from its Easter Island brethren.

This 16th-century monastery has been turned into a surrealist architecture compound.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.