This ancient tunnel is one of the most important examples of Roman hydraulic engineering in Spain.

In Spain, the ruins of a Roman military camp sit along a flooded section of a river.

A New York–based physician returned home to Spain to build his own elaborate monument to Christopher Columbus.

One of Madrid's oldest trees, with a long and colorful history, resides in El Retiro Park.

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

This panoramic lift provides a futuristic ride up San Pedro Mountain.

Despite its grandiose name, this enigmatic first-century void under the town is no cave, and it's possibly not a palace either.

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

An abandoned socialist utopia built in the late 19th century.

Religious dwelling in a Spanish volcano.

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

A neighborhood park in the city of Cáceres hides what some believe are revolutionary examples of Neanderthal cave art.

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

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

An enchanting landscape of ancient sandstone structures eroded into otherworldly shapes.

The ruins of a 2,000-year-old Roman fishing village perched on one of the best beaches in Spain.

Peek into a cave of giant, glimmering crystals.

A spectacular walk on the flank of a gorge.

The largest medieval water tank on the Iberian Peninsula is preserved beneath the Cáceres Museum.

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

This underwater graveyard commemorates a group of murdered 16th-century missionaries.

This huge abandoned fortress hidden inside a mountain holds a world of subterranean secrets.

This 19th-century fountain's namesake animal isn't what you think it is.

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