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

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

A landscape decorated with enormous skull sculptures.

A Spanish forest is filled with mysterious stone carvings.

One of Europe's largest supercomputers is housed inside of a disused chapel.

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

A whimsical brother of the nearby Fallen Angel statue takes the falling part quite literally.

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

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

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

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

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

Bacteria and algae give the salty water its bubblegum hue.

Hundreds of stone stairs and a winding medieval bridge connect this haunting Spanish island to the mainland.

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

Mountain where Jesus was first tempted by the Devil.

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

This cemetery features modernist statues as strange as its name.

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

A beautiful but toxic fountain of mercury.

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

Three bridges and one giant canyon make up this fantastic Spanish settlement.