Rudolf Höss
In June 1941, Höss met with SS Commander Heinrich Himmler in Berlin.  Himmler told Höss that Hitler had given the order for the Final Solution - to kill all of the Jewish people.  Himmler had chosen Auschwitz as the place where Europe's Jews would be exterminated.  He chose Auschwitz "[because] of its easy access by rail [train] and also because the extensive site offered space for measures ensuring isolation."  This meant that Auschwitz was big enough that the genocide of the Jews could be kept secret.  Himmler described the project as a "secret Reich matter."  Höss later said that "no one was allowed to speak about these matters with any person and that everyone promised upon his life to keep the utmost secrecy."