Two geological phenomena in one precarious locale: a towering stone window, and a deep blue void.

Italian cave with exceptional acoustics and an unsavory history.

Every inch of this chapel is covered in craftsmanship from across the world.

Vibrant street art created with mixed media.

Of the many chalices in the running for the Holy Grail, this one in Valencia Cathedral sure looks the part.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

An ancient Egyptian temple in the middle of Madrid, Spain.

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.

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

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

Mosaics created from 11 million cigar bands.

A Dutch clog company in the town of Zaandam loves the wooden shoes so much it made a museum for them.

The former home of a mad diplomat is said to still be marked in bloody, arcane scrawls.

Every equinox this Maya pyramid puts on a spooky ancient light show.

Daily jousts and dancing barrel makers in Munich's mechanical clock.

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

This legendary city has been a tourist attraction for centuries.

The hallucinogenic center of the ancient world.

Feed it cash, get your very own gold bar.

Whitewashed mosque contains the world's largest carpet.