Sonnenstein Castle The Sonnenstein castle is a castle in Pirna , near Dresden , Germany . It housed a mental hospital , which operated from 1811 to the end of World War II in 1945 . During the War , it functioned as an extermination centre for the Third Reich Action T4 program . It was shut down following the war , and reopened in 1970 . History . Sonnenstein castle , located at Pirna near Dresden , above the river Elbe , was built after 1460 on the site of a former medieval castle . Sonnenstein castle was used as a mental home since 1811 . Among other patients Sonnenstein was the asylum in which Daniel Paul Schreber wrote his Denkwürdigkeiten eines Nervenkranken in 1900 - 2 . Because of the advanced methods practiced there , it received worldwide acclaim and served as a model for other institutions . Sonnenstein Asulum was one of the first ' therapeutic asylums ' activity rooms included billiards and music rooms . Nazi era . From early 1940 , until end of June 1942 a part of the castle was converted into a killing centre . 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 while a high hoarding ( billboard ) was erected on the other sides . Four buildings were located inside the shielding . They were used for offices , living rooms for the personnel etc . Sleeping quarters for the men who burned the bodies were provided for in the attic of building C 16 . It is possible that other sections of the buildings were also used by T4 . From end of June 1940 until September 1942 approximately 15 , 000 persons were killed in the scope of the programme and the Sonderbehandlung 14f13 . The staff consisted of about 100 persons . One third of them were ordered to the extermination camps in occupied Poland , because of their experiences in deception , killing , gassing and disposing of prisoners . During August / September 1942 the Sonnenstein killing centre was liquidated and incriminating installations such as gas chambers and crematorium ovens dismantled . From October 1942 the buildings were used as a military hospital . Aftermath . In the summer of 1947 some Action T4 members appeared as accused in the Dresdner Ärzteprozess ( Doctor ' s Trial in Dresden ) . Professor Paul Nitsche , medical chief of T4 , and two male nurses from Sonnenstein were sentenced to death . It took about 40 years to recognise the part Sonnenstein played in the T4 program , and in 1989 the public commemorated the history of the centre . On 9 June 2000 a memorial center for the T - 4 Program was opened in the house . It is managed by the " Stiftung Sächsische Gedenkstätten zur Erinnerung an die Opfer politischer Gewaltherrschaft " ( Foundation for Memorial Institutions in Saxony for the Victims of Tyranny ) . Since 1970 , the building has again housed disabled people . After the establishment of a rehabilitation center , a workshop for disabled people was opened in 1991 . Bilfinger Berger worked on the refurbishment of Sonnenstein Castle in a project completed in 2011 . Literature . Stiftung Sächsische Gedenkstätten zur Erinnerung an die Opfer politischer Gewaltherrschaft ( ed . ) , " Pirna - Sonnenstein : Von einer Heilanstalt zu einem Ort nationalsozialistischer Tötungsverbrechen " ( 2001 ) . ISBN 3 - 934382 - 02 - 9