UN Secretary-General Ban Ki-moon visited the site of Nazi death camp Auschwitz on Monday to pay tribute to Holocaust victims.Ban Ki-moon visited Auschwitz, the first of two camps set up in neighboring towns Oswiecim and Brzezinka. He walked under the inscription "Arbeit Macht Frei" (Work makes you free) above a gate which prisoners passed on their way to their barracks. Ban said "nothing can truly prepare one for this epicenter of evil, where systematic murder unique in human history reached its atrocious climax."During his visit, Ban also saw exhibitions documenting the lives of the inmates and the conditions they suffered."The world must never forget, deny or downplay the Holocaust. We must remain ever on our guard," Ban said during his visit.The UN chief vowed to safeguard the testimony of Holocaust survivors "so their legacy will never die.""We will continue to shine a light on these unspeakable crimes so that they [may] never be repeated."Some 1.5 million people, mostly Jews but also Roma, Poles and others, died in gas chambers or from starvation and disease in Auschwitz and the neighboring Birkenau death camp in Nazi occupied Poland between 1940 and 1945.This was the first visit by Ban Ki-moon to Auschwitz; the last UN Secretary General to visit the former death camp was Boutros Boutros-Ghali in 1995.