This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

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

The earliest known map to show America, discovered by accident at a Paris bookshop.

Village situated on a narrow volcanic escarpment.

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

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

This house's itty bitty size means no humans allowed.

A landscape decorated with enormous skull sculptures.

The morbid items in this small and hidden museum are not for the weak stomached.

A Spanish forest is filled with mysterious stone carvings.

These magnificent city walls rise from the barren sun-baked Spanish plains like something straight out of a fairytale.

This whimsical winery by Antoni Gaudí looks ripped from the pages of a fairytale.

A museum dedicated to the Spanish occult in a town that was terrorized by the Inquisition.

Bacteria and algae give the salty water its bubblegum hue.

A lush indoor jungle fills this bustling Madrid transportation hub.

An architect transformed this abandoned cement factory into his castle-like workshop.

Abandoned for decades, trains still pass through the now-restored remains of one of Madrid's first metro stations.

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

Gaze upon chocolate sculptures depicting everything from chariot races to Gaudí's famous church at this shrine to sweets.

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

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

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

This Romanian village may have been drowned, but it is long from forgotten.

Home of the first female Hungarian poet, where her secret writing lay hidden for over a century.