Pope Francis on Friday walked alone through the notorious wrought-iron "Arbeit Macht Frei" gates at Auschwitz-Birkenau beginning a historic visit to the former Nazi death camp.
His head bowed, the pope prayed in silent contemplation before meeting Holocaust survivors in front of the death wall where the Nazis summarily shot thousands of people.
The Argentine pontiff will lead prayers for the 1.1 million mostly-Jewish victims murdered at the camp and has said that rather than making a speech he will stand in silence to reflect on the horrors committed and let his tears flow.
After arriving Wednesday in Poland -- the heartland of Nazi Germany's atrocities -- the pontiff said the world had been plunged into a piecemeal third world war.
He has repeatedly denounced those committing crimes in the name of religion, after Europe suffered a string of deadly jihadist attacks.
The pontiff, who has forged ever-closer ties between the Catholic Church and Jews since his election in 2013, will meet 12 former inmates at the site which is now a memorial and museum.
As the morning rain subsided and the sun began to shine, around 200 people gathered by a big screen in Birkenau to await his arrival, among them a group of elderly Poles known as the "righteous among the nations" who risked their lives to help hide and protects Jews.
Among those who will meet the pope are a 101-year-old woman violinist called Helena Dunicz Niwinska who played in the Auschwitz orchestra as a prisoner, alongside others who worked at the camp hospital or who were there as children.
During the visit, prayers will be said just a stone's throw from the ruins of one of the crematoriums which was blown up by the Nazis as they evacuated the camp.
Francis will also pray in the cell where Polish priest and saint Maximilian Kolbe died after taking the place of a condemned man.
The visit falls on the 75th anniversary of the day Kolbe was sentenced to death.
Poland's Chief Rabbi Michael Schudrich welcomed the pontiff's intention to remain silent during his visit to the camp, saying "often people go to Auschwitz... and they are silent (about the horrors) for the rest of their lives".
"Instead, once we leave Birkenau we must spend the rest of our lives screaming, yelling and fighting all kinds of injustices," he said Thursday.
The pope will travel the two miles (three kilometres) to Birkenau, the main extermination site, and be driven along tracks laid in 1944 to allow trains of prisoners to be transported right to the gas chambers and crematoria.
There, some 25 Christian Poles who risked their lives during the war to help hide and protects Jews -- a group recognised by Israel's Yad Vashem as "Righteous Among the Nations" -- will recount their stories to the pope.
Among them will be Maria Augustyn, whose family hid a Jewish couple behind a wardrobe for years, and Anna Bando, who helped rescue an orphan from the Warsaw ghetto and gave several Jews forged "Aryan" papers.
The Holocaust is an extremely delicate subject in Poland, where locals fuelled by anti-Semitism were accused of butchering Jews or delivering them to the Nazis.
Those who did help sometimes paid the ultimate price.
A Hebrew prayer for the dead will be read aloud in Polish by Stanislaw Ruszala, Catholic parish priest of the town of Markowa, where a family was wiped out after they were discovered to be sheltering Jews.
Jozef and Wiktoria Ulma and their seven children were butchered. Wiktoria, who was seven months pregnant at the time, had started giving birth before she was executed, according to the Vatican.
More than 100,000 non-Jewish Poles, Roma, Soviet prisoners of war, homosexuals and anti-Nazi partisans also died at the Auschwitz-Birkenau camp in occupied Poland. The Soviet Red Army liberated it in 1945.
Two of the pope's predecessors also visited the camp: John Paul II -- a former archbishop of Krakow -- in 1979 and Benedict XVI in 2006.