Hundreds of stone stairs and a winding medieval bridge connect this haunting Spanish island to the mainland.

An architect transformed this abandoned cement factory into his castle-like workshop.

If you like Art Deco you will love this bridge.

This exhibition space designed to look like the skeleton of a whale is hidden underground.

This abandoned gold mine found a second life as a post-apocalyptic film set.

The hidden ruins of an old hydroelectric plant reclaimed by nature.

Moorish signal station on a stratgic rocky outcrop.

This remote location of this Moorish stronghold means it doesn’t attract many tourists—and that it still has the aura of fear and bravery of the 1300s.

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

The ruins of an ancient stadium that hosted gripping chariot and horse races.

The fragmented remains of a massive public bath connected to the city's water supply.

An abandoned airport in the middle of nowhere.

This spectacular bridge is part of an abandoned train line that once connected Mallorcan capital to the southeastern coast.

This "flat geyser" bubbles up out of the ground periodically like a disappearing river.

The largest prehistoric cemetery on the Balearic Islands dates back over 2,500 years.

This forgotten building was one of the few Philadelphia-area breweries to survive Prohibition.

This Philly landmark has a giant butterfly pavilion, three floors of insect displays, and withstood a $40,000 heist.

The abandoned coal loading dock is a canvas for unsanctioned art.

This little-known Revolutionary War fort is supposedly haunted by the ghosts of its past.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

Site of one of World War I's most horrific scenes.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

This German art chapel is perfect for those who like their worship hard, modern, and utterly alien.

In a divided Germany, Potsdam's "central" train station was relocated to the city's southern suburbs to avoid West Berlin.