The Hartheim killing centre (German: NS-Tötungsanstalt Hartheim, sometimes translated as "Hartheim killing facility" or "Hartheim euthanasia centre") was a killing facility involved in the Nazi programme known as Aktion T4, in which German citizens deemed mentally or physically unfit were systematically murdered with poison gas. Often, these patients were transferred from other killing facilities such as the Am Spiegelgrund clinic in Vienna. This was initially a programme of "involuntary euthanasia" permitted under the law ostensibly to enable the lawful and painless killing of incurably ill patients; these murders continued even after the law was rescinded in 1942. Other victims included Jews, Communists and those considered undesirable by the state. Concentration camp inmates who were unfit for work, or otherwise deemed troublesome, were also executed here. The facility was housed in Hartheim Castle in the municipality of Alkoven, near Linz, Austria, which now is a memorial site and documentation centre.