Marzahn was the site of a labour camp (today a water treatment plant), where Roma were interned from July 16, 1936 on, two weeks prior to the 1936 Summer Olympics in Berlin, away from visitor's eyes. As a part of the Nazi "Porajmos" extermination policy, up to 2000 inmates remained there until in 1943 they were deported to Auschwitz-Birkenau, where most of them were gassed. In 1941 the large factory of the "Carl Hasse & Wrede" machine tool company (now Knorr-Bremse) was erected, where hundreds forced labourers were employed. The victims were buried at the nearby "Parkfriedhof", a memorial marks the site.