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

The morbid items in this small and hidden museum are not for the weak stomached.

One of the largest ossuaries in Spain is packed from floor to ceiling with bones.

A wonderful collection of fossilized dinosaurs and other creatures that roamed the landscape millions of years ago.

The cathedral of a controversial, conservative, schismatic sect that declared the Catholic Church heretical and founded its own succession of popes.

A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

Considered the birthplace of the Copper Age and Bronze Age, the river is tinted red from 5,000 years of mining.

The world's largest wooden structure.

An eerie collection of the surviving structures from a past celebration of the future.

The Roman city was the birthplace of various emperors and is home to one of the empire's most impressive architectural feats.

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

Spain's stunning solar energy plant.

An underground spring in a labyrinthine cave system, decorated with stalagmites and stalactites.

Hidden underground, a remarkable 10th-century bath complex survives virtually unaltered.

A Spanish artist builds his own castle.

An old wool-washing house filled with Fluxus contemporary art.

This enigmatic Roman tower lurks just outside Belmonte.

Houses are tucked between, on, and underneath giant boulders.

A windswept necropolis carved into the rocks overlooks the "most Portuguese town in Portugal."

This gaping hole in the middle of a remote mountain lake looks like a portal to another dimension.

A small sanctuary carved into the mountainside near the tallest point in continental Portugal.

This tower once served as a radar station during the Cold War.

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

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