The world’s first penitentiary, meant to be humane, drove men insane.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

One of many reminders of Tesla's scientific contributions overlooks the falls which inspired him.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

This Queens hospital has stood abandoned for almost 20 years after its patients were secretly relocated in the dead of night.

This futuristic airport terminal was abandoned for decades before reopening as a hotel—with a vintage plane of its own parked out back.

This outpost of America's most popular fast-food restaurant is housed inside a palatial mansion.

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

A formerly abandoned mental institute, now back in business.