Schloss Hartheim, or Hartheim Castle, was built by Jakob von Aspen in 1600. Hartheim Castle is quite small and there are other similar castles in the vicinity. It was donated by Prince Camillo to the Upper Austria Charity Organization as an educational and nursing home in 1898.
After World War Two, the building was converted into apartments. The gas chamber was open to visitors, beginning in 1969. Hartheim Castle is now a Memorial Site dedicated to the thousands of physically and mentally handicapped persons who were murdered here by the Nazis. Additionally, about eight thousand prisoners from the Dachau and Mauthausen concentration camps were sent here to be gassed.