Schloss Grafeneck, Memorial castle in Gomadingen, Germany

Schloss Grafeneck is a wide, rectangular building with a yellow facade and a red tiled roof pierced by small dormer windows, located near Gomadingen beside the Marbach stud farm. Three storeys face forward, each row of windows framed by green shutters; a rounded arched doorway with a double wooden door and glass panes sits at the centre of the ground floor, topped by a small relief. The building houses a documentation centre and the Grafeneck memorial.

Grafeneck Castle was used as a killing facility from 18 January 1940, when the first murders of the T4 programme took place in a gas chamber disguised as a shower room inside a "garage"; the institution's doctor let in carbon monoxide and the bodies were burned in a crematorium. After the events became public, Heinrich Himmler pushed for the facility to be closed in December 1940, and the killing continued at Hadamar. In all, 10,654 people were murdered at Grafeneck in 1940.

The name Grafeneck refers to the former hunting lodge of the dukes of Württemberg, built around 1560 on the site of a medieval castle. Since October 2005 the memorial has included a documentation centre; the "Garage" housing the gas chamber was demolished in the 1960s, so visitors today see the grounds and cemetery laid out in 1930 rather than the killing room itself.

The memorial and documentation centre occupy the former castle; the gas chamber building, called the "Garage", was demolished in the 1960s, so no original killing room remains. The site lies next to the Marbach state stud farm, about 25 km southeast of Tübingen between Engstingen and Münsingen. The castle is still used by a disability and social psychiatry institution, so parts are not open to visitors.

The gas chamber disguised as a shower room stood in a building called the "Garage", demolished in the 1960s; no structure marks it today. The Samariterstiftung, which ran a home for disabled people here from 1928, bought the castle and laid out its own cemetery in 1930.