Ban Ki-Moon toured Auschwitz today, marking the UN general secretary’s first visit to the notorious Nazi camp.

Accompanied by Marian Turski, an 87-year-old Holocaust survivor, and Tel Aviv Chief Rabbi Israel Meir Lau, Ban spent time viewing public exhibits and barracks, stopping to lay a wreath in front of a wall where Nazi prisoners were systematically shot and killed.

“I stare at the piles of glasses, hair, shoes, prayer shawls and dolls, and try to imagine the individual Jews and others to whom they belonged,” Ban said. “I stand in disbelief before the gas chambers and crematorium — and shudder at the cruelty of those who designed this death factory.”

“Auschwitz-Birkenau is not simply a register of atrocities. It is also a repository of courage and hope. Today I say loud and clear: Never again,” he added.

Auschwitz is arguably the most nefarious of the Nazi death camps, with 1 million Jews killed along with 100,000 non-Jewish Poles, Roma, Soviet prisoners of war and anti-Nazi protestors.

“I pay my deepest tribute to the victims and survivors of the Holocaust, a most terrible horror in human history,” the UN head wrote in the memorial book at the site’s museum.

“The United Nations is strongly committed to the vital work of Holocaust remembrance and education, and to building a world of equality and dignity for all.”

Ban is just the second UN leader to visit Auschwitz—Boutros Boutros Ghali also visited in 1995.

Ban made the trip after a visit to Lithuania, which currently holds the rotating half-year seat of the EU presidency. He will spend three-days in Poland, making an appearance at the UN climate talks in Warsaw and meeting with Polish Prime Minister Donald Tusk and President Bronislaw Komorowski.