The first assassination city was the extermination camp of Chelmno, in Poland, where was the trial for the first occurrences of gas killings were performed. Chelmno started to kill whole extradition trains from November 1941 on. Then reached Belzec, Sobibor, Auschwitz, Maïdanek, and Treblinka. The extermination camps performed a fundamental function in the Holocaust.