Rippling sand dunes frozen in the Arizona rock.

Sanctuary on a ridge near an ancient shrine to a "Black Madonna" built by the founder of Opus Dei.

Giant topiary dog once played a role in a terrorist bomb plot.

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

A darkly erotic open-air statuary in Catalonia.

Abandoned Nazi train station turned underground astroparticle laboratory.

A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.

A gravity-defying "devil's bridge" that has a surprising architectural feature for its stability.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

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.

This former Baroque palace on the historic Calle Montcada is a rare architectural gem and was once the meeting place of an aristocratic scholarly society.

At the foot of a waterfall lies a peaceful swimming lagoon and evidence of over 60,000 years of human habitation.

Village situated on a narrow volcanic escarpment.

32,000 tiny soldiers are posed in 23 historical settings.