An outsider folly near Madrid.

One of Europe's largest groups of dolmens remains largely off the typical tourist track.

The extensive relics of an ancient Roman and Phoenician fish processing plant hide in a town park.

Abandoned tunnels dug for the once-thriving sea salt industry on the coast of southern Spain.

Religious dwelling in a Spanish volcano.

The ruins of a bombed medieval village memorialize the destruction of the Spanish Civil War.

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

This Arab fortress was once the largest citadel in Western Europe.

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

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.

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

This 7,000-year-old megalithic wonder covered by a Franco-era reservoir emerges in times of drought.

These primitive rock paintings include a very beloved depiction of a woolly mammoth.

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

A hidden medieval crypt where a famous legend says the devil used to teach black magic.

This unassuming bookstore in the heart of Madrid is one of the oldest in Spain.

The atmospheric ruins of a historic church can be found on a hill above the city of Oviedo.

Now a pile of ruins and rubble, this was a lovely mountain town as recently as 1960.

A magnificent, long-abandoned castle built in the wake of the reconquest of Spain.

A spectacular walk on the flank of a gorge.

A unique exhibit lets blind people experience famous works of art and architecture with their hands.

A well-restored ancient archaeology site gives a real feel for life during the Roman age.

The walls of these four caverns are filled with art that dates back to the earliest human presence in Europe.

This surreal-looking tree pruned more than 1,000 years ago is still producing olives for oil.