This beautifully verdant lagoon is tucked below a massive volcano in a crater atop a black pebble beach.

This mountaintop observatory is home to one of the world's largest reflective telescopes.

According to the Guanches, the aboriginal people of the Canary Islands, the king of evil lives inside this volcano.

A series of recreated fortifications mark George Orwell's path through the Spanish Civil War.

Earth's rocky history has rarely glittered so brightly as it does in this Spanish museum.

This religious complex carved into a cliff is steeped in legends of miraculous stags and the Holy Grail.

This ancient Spanish castle sits high upon a hilltop.

Devastated landscape used for hundreds of years by the Romans as their primary mining site.

Mine shafts and hard pastries await visitors at this massive mountain of salt.

A completely underwater art museum sends a stark message about humans' impact on the environment.

Moorish signal station on a stratgic rocky outcrop.

A site where “the ravages of the war are more striking…than any other place in contemporary Spain.”

Considered the birthplace of the Copper Age and Bronze Age, the river is tinted red from 5,000 years of mining.

This awesome Spanish castle is so fantastical it was actually used on Game of Thrones.

Giant eggs, walls of bread, and nightmare surreality mark the largest collection of works by Salvador Dalí.

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

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

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

A Spanish town built into the cliffs.

An enchanting monastery in the Spanish countryside appears lifted from a fantasy tale.

The university library shaped like a giant piece of Swiss cheese.

This long line of cement defensive wedges is named after the famous chocolate bar for obvious reasons.

This secret Swiss fortress is disguised as a harmless pink house, complete with fake windows.

Over 3km of caverns and caves at the Switzerland-France border contain the largest underground river in Central Europe.