Partially collapsed lava tube and cave system complete with concert hall, underground pond, and unique albino crabs.

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

This magical space partly designed by Antoni Gaudi is one of the best examples of romantic gardening in the Mediterranean.

The little church's beautifully frescoed ceiling has earned it the nickname “the Sistine Chapel of Madrid.”

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

The chefs at El Diablo use heat generated by an active volcano to cook the food.

The abandoned ruins of a beautiful medieval castle just outside Barcelona.

A once grand hotel now sits eerily abandoned in the Catalan countryside outside Barcelona.

Stunning Roman aqueduct used for 1900 years and still standing.

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

A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.

This awesome Spanish castle is so fantastical it was actually used on Game of Thrones.

The only urban monument in the world designed by the great surrealist painter Salvador Dalí.

This Navarrese cave's history of witchcraft and pagan ritual is not just embraced, but recreated each year.

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

A gravity-defying "devil's bridge" that has a surprising architectural feature for its stability.

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

Giant eggs, walls of bread, and nightmare surreality mark the largest collection of works by Salvador Dalí.

This amazing abuela became a diehard metal fan late in life and an icon of Madrid's '80s rock scene.

These magnificent city walls rise from the barren sun-baked Spanish plains like something straight out of a fairytale.

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

At the foot of a waterfall lies a peaceful swimming lagoon and evidence of over 60,000 years of human habitation.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

An enchanting monastery in the Spanish countryside appears lifted from a fantasy tale.