The sheer scale of the death camp used to murder more than a million people during the Holocaust is laid bare in this astonishing footage.
The Auschwitz-Birkenau complex in Poland is where an estimated 1.1 million Jews and others were transported by train and murdered in gas chambers before the Soviet Army liberated it 70 years ago today (Tuesday).
As world leaders prepared to gather there to mark Holocaust Memorial Day, a drone flew above it to capture the size of the former death camp, showing the rows of huts where people were crammed and the chimneys of crematoriums where its victims' bodies were burned.
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The footage, provided by ITN, shows the fences, guard towers and the infamous words 'Arbeit Macht Frei' (work makes you free) on the entrance gate.
The horror of what happened is difficult to understand but the footage shows the scale of infrastructure needed to make it happen.
Aged Auschwitz survivors walked through camp's the gates today, holding red roses to lay wreaths at the "death wall". There will be a service and candle-lighting at Birkenau, the sister death camp in the same complex as Auschwitz.
Pope Francis tweeted:
Auschwitz cries out with the pain of immense suffering and pleads for a future of respect, peace and encounter among peoples.— Pope Francis (@Pontifex) January 27, 2015
Today's event is expected to be the last major anniversary that survivors can attend in large numbers.