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

A beautiful but toxic fountain of mercury.

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

This cemetery features modernist statues as strange as its name.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

This semi-secret storybook hedge maze is also the oldest garden in the city.

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.

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

One of Amsterdam's narrowest houses is located right across the canal from its widest.

Amsterdam's former hotspot for public executions and dissections.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

The largest collection of handbags in the world, the oldest of which were used to carry Bibles, primarily by men.

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

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

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

A beautifully eclectic mix of architectural styles.

The attic of a four-century-old canal house hides a clandestine church.

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

Cat art as far as the eye can see.

A curious collection dedicated to human and animal anatomy and pathology.