From early 1940 until end of June 1942, a part of the large mental asylum within Sonnenstein Castle was converted into a euthanasia killing center: the Sonnenstein Nazi Death Institute. It was a testing ground for initial development of certain methods, later generally adopted and refined for usage associated with the Final Solution. A gas chamber and crematorium were installed in the cellar of the former men's sanitary (building C 16). A high brick-wall on two sides of the complex shielded it from outside view. Four buildings were located inside this brick-wall shielding. They were used as offices, living rooms for the personnel, etc. Sleeping quarters for the men responsible for incinerating the bodies were provided in the attic of building C 16. It is possible that other sections of the buildings were also used by Action T4.