As just mentioned, throughout occupied Poland, the Germans gathered the Jews and forced them to live in specific city quarters called ghettos. Usually, these ghettos were surrounded by walls so that the Nazis could keep track of the Jews--it also made it easier to round up the Jews to send them to the death camps.  This is the ghetto wall in Krakow, one of the oldest cities in Poland and located on the Vistula River in the south of Poland.  It was the capital of Germany's General Government during World War II.  Within the ghetto, there were gathered tens of thousands of Jews.  Nearby was the camp at Auschwitz.