"Satisfying" is a good way to describe these beautifully aligned rows of Spanish mills.

An arresting arch punched straight through a mountain provides one of the most scenic spots, and challenging climbs, on the planet.

Hundreds of caves once used to store grains and animal feed.

Abandoned 18th century weapons factory in the Aezkoa Valley.

This abandoned, turn-of-the-century astronomy hub is now the subject of more photographs than it ever took.

Part of the medieval watchtower is displayed in an otherwise ordinary parking garage.

An ornate tower shows off a local artist's architectural flair.

Lava stone structures possibly dating back to the 19th century may have been a stopping point for voyagers between ancient Egypt and the Mayan Civilization.

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.

This 47-story "M" needed 20 years to be completed

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

This underground church is topped with a 500-foot cross that is seen by many as a beacon of fascist hubris.

An archeological treasure trove stumbled upon by a couple of children.

A contemporary art installation housed within a Gothic cathedral.

Haunted tuberculosis hospital built by the patients.

A five-square-mile slice of Spain on the Mediterranean coast of North Africa.

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

A micro-communist utopia in Spain with no police, no mortgages and full employment.

The Gaudí-inspired building that was the start of Terrassenc modernism.

12th-century holy complex shares land with a natural park full of heavenly waterfalls and raptors.

Stuck in the middle of a modern Madrid city block are the remains of a 19th century sports complex.

This chest hospital with a dark, haunted past serves as a fitting set for horror films and a paradise for ghost hunters.

A network of hundreds of interconnected wineries in caves hides under the town center.