Concentration camps were places where the Nazis imprisoned and killed millions of Jews, Gypsies, and others during World War II. The camps held people in cramped and unsanitary conditions, where many died of disease, starvation, overwork, or were victims of medical experiments. The largest camp was Auschwitz, where over 1 million people were killed through gas chambers, medical experiments, starvation, or exhaustion from slave labor. Other major camps included Buchenwald, Dachau, Sachsenhausen, Treblinka, and Theresienstadt, where prisoners suffered and died from harsh conditions, executions, lack of food and medical care.