Austria's Josef Fritzl hid his underground dungeon—in which he imprisoned his daughter and three of their children—so well that police couldn't find it without his hands-on help. The BBC pieces together a look at the 650-square-foot area in his cellar that Fritzl used to hide his secret family. He got into the dungeon via a 3-foot concrete door hidden beneath shelves in his cellar workshop—and only he could open the electronic lock.
The dungeon area was divided into rooms—some no bigger than about 5 feet high—for sleeping, cooking, and bathing. Fritzl expanded the dungeon as the second family grew, though police are curious how he did so secretly. The four occupants never got fresh air, but a tube provided ventilation. To cover his tracks, Fritzl forbid his wife and children living upstairs from entering the cellar.