On Tuesday 27 January 2015, European heads of state and former inmates of Auschwitz will commemorate the 70th anniversary of the camp's liberation.

Nazi Germany murdered approximately 1.1 million people at Auschwitz, mostly Jews, but also Poles, Roma, Soviet prisoners of war and gays.

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Railway tracks lead to the former Nazi concentration camp Auschwitz-Birkenau, near Oswiecim in PolandKacper Pempel/Reuters
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The sign "Arbeit macht frei" (Work makes you free) is pictured at the main gate of AuschwitzKacper Pempel/Reuters
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Security lights illuminate the barbed wire perimeter fence of the Auschwitz I extermination campChristopher Furlong/Getty Images

The anniversary raises painful questions for residents of Oswiecim, the town in Poland where Nazi occupiers created one of the most relentless extermination machines in history.

How could their parents go about their daily business when such inhumanity was taking place just the other side of a barbed wire fence? How much did they know of what was going on?

"Of course people knew what was going on," said Bogumila, who lived through the occupation as a child. The mass extermination of prisoners and the incineration of thousands of bodies, she said, were no secret.

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Prisoners' suitcases are exhibited in the cell blocks of the Auschwitz I extermination campChristopher Furlong/Getty Images
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Prisoners' shoes are displayed at the former German Nazi concentration and extermination campPawel Ulatowski/Reuters
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Artificial limbs that belonged to people brought to Auschwitz for exterminationPawel Ulatowski/Reuters
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Glasses that belonged to people brought to Auschwitz for exterminationPawel Ulatowski/Reuters
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Some of the personal photographs taken from prisoners as they arrived at the Auschwitz II Birkenau extermination campChristopher Furlong/Getty Images
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Empty canisters of Zyklon B, a pesticide used by Nazis to execute Jews, are displayed at AuschwitzPawel Ulatowski/Reuters

Some describe having to live with the stench from bodies being incinerated at Auschwitz, but keeping quiet to survive.

Between 1940 and 1945, Auschwitz developed into a vast complex of barracks, workshops, gas chambers and crematoria.

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Dawn breaks over an accommodation block at the Auschwitz II Birkenau extermination campChristopher Furlong/Getty Images
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Prisoners' bunks line the inside of a block at the Auschwitz II Birkenau extermination campChristopher Furlong/Getty Images
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Sleeping places for prisoners are seen in a barracks at Auschwitz BirkenauKacper Pempel/Reuters
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Visitors look at a 'wall of death' at the former German Nazi concentration and extermination campPawel Ulatowski/Reuters
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A crematorium at the former Nazi death camp of Auschwitz BirkenauYves Herman/Reuters
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'The Little Wood' – where prisoners were held waiting before they entered the gas chambers at the Auschwitz II Birkenau extermination campChristopher Furlong/Getty Images

Seven decades on, Oswiecim is trying to put the bleak past behind it, a giant "City of Peace" banner displayed next to the main railway hub, which once saw hundreds of thousands transported in cattle wagons into the camp's gas chambers.