Ravensbrück concentration camp
In early 1945, the SS made prisoners build a gas chamber at Ravensbrück.  By this time, the Nazis knew that the Soviet Red Army was getting close.  They wanted to kill as many prisoners as possible before the Red Army arrived.  In its last few months, Ravensbrück became an extermination camp (a death camp).  The SS started sending children and prisoners from Ravensbrück's sub-camps to the main camp, so they could be gassed to death.  In just a few months, the SS killed 5,000 to 6,000 prisoners in the gas chamber.