Although 90 percent of the material held by the Arolsen Archive has now been digitised, the complex still stores some 30 million original documents on almost 17.5 million people.
There are also thousands of items such as watches, rings and wallets collected from the old Nazi camps.
The archive was originally set up by the Allies in early 1946 as the International Tracing Service to help people find relatives who had disappeared during the war.
It mostly dealt with Jews but also Roma, homosexuals, political dissidents and “racially pure” children kidnapped by the Nazis as part of a programme to address the falling birth rate.
Bad Arolsen was chosen because it had escaped Allied bombing and had a working telephone network, and because of its location at the centre of Germany’s four occupation zones (French, American, British and Soviet).
At first the service was run by a curious mix of members of the Allied forces, Holocaust survivors from all over Europe and Germans — including former members of the Nazi party.
But from the 1950s onwards, as many of the survivors left the country, German staff numbers increased.
Today, the archive has around 200 employees, assisted by some 50 volunteers around the world.
And it is still handling around 20,000 enquiries per year, according to Azoulay, often from children or grandchildren of victims or survivors who want to know what happened to them.
Like Abraham Ben, born to Polish-Jewish parents in a displaced persons camp in Bamberg, southern Germany, in May 1947.
No grandparents