Rare karst landscape eroded from a flat seabed.

The world's first electric battery-powered submarine.

This massive fiberglass Gulliver turns every visitor into a Lilliputian.

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

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

Abandoned Nazi train station turned underground astroparticle laboratory.

Giant topiary dog once played a role in a terrorist bomb plot.

Natural stone arches form a walkable "cathedral" at low tide, then disappear entirely when the water returns.

The oldest Roman lighthouse still in use.

Open air sculptures by an eccentric and loin-clothed hermit.

This abandoned naval battery stood at the ready as recently as the 1980s.

Remarkably intact Roman stone fortifications have encircled this Spanish city for centuries.

An accidental trick of light casts the perfect shadow of a pilgrim of the Camino de Santiago against the cathedral wall.

Seaside ruins of a settlement that date back to the first century B.C.

A 12th century church completely covered in shells.

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

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

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

An ancient Egyptian temple in the middle of Madrid, Spain.

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

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

The Cathedral of Salamanca has a number of unusual carvings but none so surprising as a modern astronaut.

The gaunt visage of this angular Christ giant is enough to put the fear of God into all who see it.