Auschwitz was a network of concentration and extermination camps built and operated in occupied Poland by Nazi Germany during the Second World War. It was the largest of the German concentration camps. From spring 1942 until the fall of 1944, transport trains delivered Jews to the camp's gas chambers from all over Nazi-occupied Europe and nearly three million people had died there. On January 27, 1945, Auschwitz was liberated by Soviet troops, a day commemorated around the world as International Holocaust Remembrance Day. In 1947, Poland founded a museum on the site of Auschwitz I and II, which by 1994 had seen 22 million visitors—500,000 annually—pass through the iron gates crowned with the infamous motto.