Gas chambers were created to mass kill off jewish people and anyone who didn't fit aryan race. The germans used Zyklon B pellets mixed with water too steam the room up and kill the jews. After the jews were gassed they were taken too an oven and burnt or they were burried in mass graves. Some of the biggest gas chambers were located at Auschwitz in Poland.
This is a gas chamber in Auschwitz. I chose this because this is a very good visual of what exactly the Jewish people saw before they were gassed.
This is a video of a gas chamber in Auschwitz. This video tours the inside of the gas chambers.