The house, until this year, had always been in private hands. A U.S.-based group, the "Counter Extremism Project," has purchased it. Now, in conjunction with the Auschwitz Museum and UNESCO, they have created "The Auschwitz Center on Hate, Extremism and Radicalisation." The home is now open to the public for the first time.

By Barbara Erling and Kuba Stezycki OSWIECIM, Poland (Reuters) -Auschwitz survivors were being joined by world leaders on Monday to mark the 80th anniversary of the liberation of the Nazi German death camp by Soviet troops,

“God suffered a great deal in every single person who was here. God suffered a great deal in this place,” Cardinal Rys added.

Auschwitz concentration camp is a symbol of the Holocaust in southern Poland, one of the most trying moments in human history.

In just over four-and-a-half years, Nazi Germany systematically murdered at least 1.1 million people at Auschwitz, built in the south of occupied Poland near the town of Oswiecim. Auschwitz was at the centre of the Nazi campaign to eradicate Europe's Jewish population, and almost one million of those who died there were Jews.

It doesn’t do any good for your heart, for your mind, for anything,” said Holocaust survivor Jona Laks, 94, about her return to Nazi Germany’s Auschwitz-Birkenau concentration camp.

Auschwitz survivors have warned of the rising antisemitism and hatred in the modern world as they gathered with world leaders and European royalty on the 80th anniversary of the death camp’s liberation.

The ceremony is widely regarded as the last major observance likely to see a significant number of survivors in attendance.

Silence pervades the site of Auschwitz-Birkenau today. Sometimes the only sounds are the soft footsteps of visitors, people who come from all over the world to mourn and to learn, and the voices of their guides speaking in hushed tones into microphones trying to explain the ungraspable.

In all, the Nazi regime murdered 6 million Jews from all over Europe, annihilating two-thirds of Europe's Jews and one-third of all Jews worldwide. In 2005, the United Nations designated Jan. 27 as International Holocaust Remembrance Day.

Jan. 27, marks International Holocaust Day. NBC News' Jay Gray reports from Auschwitz, where the 80th anniversary of its liberation will bring forth memories and messages that resonate today.