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

This abandoned dream castle and its cemetery look out over the city that once inspired their creation.

Standing in a state of "arrested decay," this ghost town allows for a detailed peek into Gold Rush life in an unusually harsh climate.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

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

Terrifying derelict military hospital once housed a recuperating Hitler.

This recently restored crypt was once plagued by liquefying coffins and exploding caskets.

The concrete shell of an industry giant remains as a playground for graffiti artists, auto scrappers, and paintball warriors.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

A kaleidoscopic warehouse-maze of handmade neon signs.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

A tunnel once abandoned now thrives with graffiti art as an off-limits makeshift gallery.

World War II-era Nazi compound nestled in the Santa Monica hills.

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