An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

The vast chamber inside this abandoned cooling tower looks like something out of a sci-fi dystopia.

A collection of weird and wonderful art fills a former houseplant nursery.

Nature is slowly overtaking this disused cemetery on the outskirts of Brussels.

Part modern art project, part traditional chapel, this see-through church is only substantial from the right angle.

This abandoned mansion has a window for every day of the year, and is a temple for ghost hunters.

The history of this Moorish castle includes royals, a Mexican-Spanish association, and several attempts at lodging.

A large collection of solar and night-time telescopes dot a small area on the Teide mountain range.

The magnificent sanctuary is Spain's first purpose-built structure of its kind.

These Bullet-scarred bunkers are haunting reminders of the Spanish Civil War.

The last of three massive blast furnaces that were once at the foundation of the Port of Sagunto economy.

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

The 20th-century church looks like a rustic version of the Sagrada Familia.

An unexpected ghost village lurks on the southeast coast of Tenerife.

For decades, Puerta del Sol has been illuminated by a giant, guitar-wielding bottle of sherry.

To fit bodies into this Renaissance crypt, they were first left to decompose in the crypt's rotting room.

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

Medieval ruins nestled within a breathtaking swath of Spanish nature.

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

The ruins of an ancient Celtiberian town with incredible rock-cut buildings and a Roman aqueduct.

Rumors and legends of secret Nazi activities surround this eerily remote island mansion.

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

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

An outsider folly near Madrid.