Seventy-five years after the liberation of the biggest Nazi death camp, survivors and leaders recall the horrors of the Holocaust.

Holocaust survivors and world leaders gathered at the site of the former Auschwitz-Birkenau Nazi death camp in southern Poland on Monday to mark the 75th anniversary of its liberation at the end of World War II.

More than 100 former prisoners of the biggest Nazi extermination camp attended a wreath-laying ceremony and remembered the more than 1.1 million men, women and children who perished there.

The Auschwitz-Birkenau complex was liberated by the Soviet Red Army on January 27, 1945 and become a symbol of Nazi Germany’s systematic murder of some six million Jews — around two-thirds of Europe’s Jewish population.

It is estimated that 1.3 million people were sent to Auschwitz. Those who died there included 960,000 Jews, 74,000 non-Jewish Poles, 21,000 Roma people, 15,000 Soviet prisoners of war and up to 15,000 other Europeans.