Joseph Fritzl’s plot to imprison his daughter began when the girl was just 12, Austrian police believe, six years before he finally locked her away. Fritzl built an extension to his house between 1978 and 1983, AFP reports. “The intention must have been there to build a secret area, a small dungeon,” said the chief investigator.
It was only after Elisabeth Fritzl bore her first child in 1993 that Fritzl expanded the prison, breaking into unused cellar rooms beneath the house’s oldest sections. Police also found a half-ton concrete door, which had clearly been used before the modern steel doors were installed. In all, the dungeon lay behind eight locked doors, including three with electronic combination locks.