A haunting collection of the vanished and disappearing natural world.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

World's first "penitentiary," meant to be humane, drove men insane.

Townhouse facade doubles as an RMS Titanic Memorial.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

A crumbling hospital from the 1850s on Roosevelt Island.

Underground tunnels remain beneath this abandoned mental asylum.

The haunting, dilapidated remains of a former poorhouse on Staten Island's Greenbelt.

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

Former farm staffed by mental patients is now a public park.

Beneath the mossy overgrowth covering this once-sprawling campus lies decades of history and the secrets that come with it.

This former tuberculosis research hospital endeavored to cure the dreaded disease with fresh air and positive attitudes.

A small flooded ghost town with a few scattered structures remaining.

The ghost town left by the worst nuclear disaster of all time is being taken over by nature and urban explorers.

This attraction was abandoned after the Chernobyl disaster.

An Art Nouveau building covered in animal gargoyles and grotesques.

The largest catacomb system in the world.

The curios of pharmacist and collector Henry Wellcome.

This South London cemetery holds the remains of more than 15,000 people.

An incarceration museum on the spot of possibly the oldest prison in England.

Since 1874, this macabre collection has developed into a museum devoted to Scotland Yard's mementos of dastardly deeds.

Remnants of a storybook amusement park hidden behind a strip mall.