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

One of Europe's largest supercomputers is housed inside of a disused chapel.

One of the most photographed buildings in a city known for its Modernista architecture is an abandoned squat.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

Mountain where Jesus was first tempted by the Devil.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

Two planes stand abandoned after the closure of an aircraft-themed restaurant.

The abandoned "Ghost Mansion" was left to decay in the mountains of Northern Italy.

The last planned Soviet city was built for the former residents of Pripyat after the Chernobyl disaster.

This abandoned island off the Venetian coast has been a radical monastery, a political prison, and a secret Nazi base.

The plague quarantine island home to the alleged "Vampire of Venice."

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

The remains of three Luftwaffe launch pads designed for manned anti-aircraft missiles.

Remnants of a cone-shaped Nazi bomb shelter.

A collection of miniature, symbolic sculptures hides in plain sight across Kyiv.

This truly palatial work of Communist-era architecture now sits crumbling on a Croatian beach.

A scattered trail of street art adds a pop of color to the city's stark structures.

A former bank seized as a sniper vantage point during the Bosnian War is now a secret graffiti art gallery.

A domed disco abandoned since the '70s now attracts artists and explorers under its unique roof.

Now abandoned, the world's first torpedo factory is crumbling into the sea.

An abandoned Cold War missile radar site.

An abandoned bell tower in the middle of nowhere is the last testimony of a forgotten medieval village.

An abandoned 17th-century baroque hunting lodge with a wonderfully strange architectural plan.

Austria's very first and only nuclear power station was completed but never used.