A Romanesque tower appears when water levels drop.

This ancient Spanish castle sits high upon a hilltop.

Living towers made of people that are now recognized by UNESCO.

Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.

This Funeral Hearse Museum represents the finest in cadaver transportation.

This cemetery features modernist statues as strange as its name.

A former steam-powered mill from the 1800s is now an industrial park with a giant steel dragon slide.

A once-secret library of Freemason history in Catalonia.

The former 1920s mansion of a prominent Catalan developer was used as the Soviet Embassy during the Spanish Civil War, and there is still a bunker below the garden.

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

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

A temple to modernity, tucked away amid Barcelona's more well known museums.

A daily pyrotechnic celebration marks a beloved tradition during Valencia's festival season.

This massive fiberglass Gulliver turns every visitor into a Lilliputian.

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

Bold black and white motifs of life and death add a dramatic flair to this 17th-century crypt.

Elevated freight railway turned wildly successful urban park.

Manhattan’s Battery Park has a whimsical carousel full of spinning, glowing fish.

Tucked in the back of this amazing antique store is an important piece of medical history.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

17th century mosque for Shah Abbas' harem.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

The palace of the King of Kings, burned by Alexander the Great.