A forgotten monument to Yugoslavian freedom.

When Croatia became independent of Yugoslavia, the splintering governments left behind these concrete tunnels.

A girls' boarding school inspired by the Chicago World's Fair, once abandoned, now restored to strange and scenic glory.

Once a state-of-the-art tuberculosis treatment spa, these ruins are now ruled by paintball players.

North America's oldest quarantine facility was built in response to Philadelphia's 1793 yellow fever outbreak.

One artist's yard is full of shining, whirling kinetic sculptures that look like pure steel psychedelia.

This family mausoleum is steeped in symbolism and looks more like a fantasy location than a grave.

Once living up to its name as the grandest hotel in all of Africa, the Grande Hotel is now home to a community of squatters.

This stoic, if derpy, giant stands as a monument to Oregon's statehood and the novelty culture of yesteryear.

The seamy, underground secrets of Portland's criminal past.

Destroyed Serbian army headquarters sits half crumbled in a largely revitalized Belgrade.

A pair of connected skyscrapers form this symbolic gateway.

Nuclear reactor created the plutonium used on Nagasaki.

A huge musical sculpture and other art installations on the National Oceanic and Atmospheric Administration grounds.

Cave carved out of a huge snow drift collapsed killing one and injuring five in July 2015.

Train debris from the deadliest avalanche in United States history can still be found in the ravine where so many perished.

An ice cream parlor chain that caters to vegans and pinball fans equally.

An abandoned guano-mining city in the South Pacific.

This abandoned mining village was predicted to resist decay longer than any other modern human settlement.

The ruins of this Alaska gold mine form a gorgeous ghost town.

A desert ghost town—occupied for only 12 years—was once home to more than 500 silver mines.

This old mining town, deep in the California desert, has a year-round population of one.

On the outskirts of a desert trading village high on the Andean plain, steel giants have been destroyed by salt winds.

Thousands of rusting train cars have been slowly falling apart on the edge of Greece's second largest city.