A road that winds through this natural cave is the only way to access the small, appropriately-named village of Cuevas.

An Antoni Gaudí masterpiece in Astorga.

An uninhabited village that preserves and documents rural architecture and an endangered way of life.

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

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

An abandoned 6th-century monastery features a medieval map of the known world.

The ruins of the second-largest circus school in the world.

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

An abandoned mine now resembles a post-apocalyptic landscape of derelict buildings and blood-red pools of water.

This small chapel is built of human bones and decorated with a golden skeleton.

Perhaps the most spectacular grotto along the Algarve coastline.

These narrow stone granaries have been used to store and dry out grain for hundreds of years.

A stunning 18th-century site where pilgrims ascend by a series of punishing stairs only to return via funicular.

A hidden three-foot-wide house separates these two regal churches.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

Elaborate tile work in this railway station tells the story of Portugal.

This giant sculpture made of trash is a critique of society's wastefulness.

A majestic hotel for dreamers rises from the center of a fairytale wood.

These 400-year-old ruins are all that's left of the monastery where Ines de Castro was assassinated by the King of Portugal.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

A deer-headed statue that brings together a 12th-century legend and big wave surfing.

Three bridges and one giant canyon make up this fantastic Spanish settlement.