Among the oldest structures in Madrid, these Moorish walls once guarded the medieval city of Mayrit.

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

Cliffside houses provide a spectacular view from their perch above the valley.

These magnificently sculpted tombs represent Spain's own legendary version of "Romeo and Juliet."

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

Abandoned Nazi train station turned underground astroparticle laboratory.

The eclectic observatory castle of a 19th-century astronomer and explorer.

This tiny river island switches sovereignty every six months as part of a rare, centuries-old agreement.

This Navarrese cave's history of witchcraft and pagan ritual is not just embraced, but recreated each year.

Abandoned blockhouses from Nazi Germany's Atlantic Wall erode into the sea on a French beach.

This stop on the Camino de Santiago stands high above the underwater ruins of a medieval town.

This enormous censer uses a pulley system installed over 400 years ago.

Thanks to an acoustic anomaly, this unassuming stone bench has heard one hundred years of secrets.

The oldest Roman lighthouse still in use.

Two large posteriors in one giant statue.

The surviving remnants of a destroyed medieval church now stand in a public park.

A wonderful collection of fossilized dinosaurs and other creatures that roamed the landscape millions of years ago.

A road that winds through this natural cave is the only way to access the small, appropriately-named village of Cuevas.

This beautiful spit of land was once the summer playground of the king of Spain.

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

The oldest operating roller coaster of its kind, the Montaña Suiza has been thrilling riders since 1928.

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

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.