The exhibition is being held at Berlin's Potsdamer Platz

Ever since last year, when the idea for a new exhibition exploring the role of Germany's railway company during the Holocaust was first mooted, there has been a heated debate in the media.

Questions were being asked: Where should the exhibition be held - in a train station or at a more discreet location? And is Deutsche Bahn really facing up to its historic responsibility?

For the railway company, the successor to the Nazi Reichsbahn, confronting the past has been a controversial and long-drawn-out process.

Deutsche Bahn knows that it played a big and bad role in the Holocaust, but it took a long time for it to acknowledge that. Without the Bahn, no-one would have been deported to the camps Hermann Simon Berlin's Centrum Judaicum

Initially, Deutsche Bahn's head Hartmut Mehdorn said he did not want the exhibition to be held in German stations.

"The subject is too serious for people who are in a rush to get their train, or munching sandwiches," he said.

But he relented later, after coming under a lot of pressure from Jewish groups and the German government.

'Death trains'

"What was important for me was to have this exhibition in a public place, at train stations, where people are passing through all the time," German Transport Minister Wolfgang Tiefensee, told the BBC.

Reichsbahn transported some 3m people to Nazi death camps

"The Nazi dictatorship penetrated all aspects of everyday life. Of course, we had a few disagreements with Deutsche Bahn about the location of the exhibition, but we managed to resolve our differences. I would like everyone to be confronted with the question: 'How was it possible that people allowed such crimes to happen?'" he said.

The exhibition - Special Trains to Death - is being held at the station in Potsdamer Platz in central Berlin.

It is a small exhibition, comprising documents and letters which testify to the cruel efficiency with which the Nazis transported people to their death and the cold bureaucracy of Nazi officials.

In a few letters, Nazi officials cynically refer to the "movement of Jews" and "the evacuation of foreign people".

Two brothers' story

There is a collection of photographs of children who were deported, as well as personal testimonies of Holocaust survivors.

Nazi hunters Beate and Serge Klarsfeld visited the exhibition

The event also traces the plight of some of the 11,400 Jewish children who were deported from France to the Auschwitz concentration camp between 1942 and 1944. Only 2% of the children survived.

"We have given a face to these children so that their stories can be documented in the history books," said Beate Klarsfeld, from the foundation Sons and Daughters of Jews Deported from France.

On one board, there is a photograph of two brothers from Berlin, Hans and Gert Rosenthal. The youngest, 10-year-old Gert, was deported from Berlin to Riga on the "21 OstTransport" train, along with other Jewish children.

Gert was murdered in 1942. His brother Hans survived.

Booming business

At least three million people, including Jews, Sinti and Roma, were transported on the Reichsbahn from all over Germany and Nazi-occupied Europe to concentration camps, such as Auschwitz, Sobibor or Treblinka.

Thousands of trains carried people to the extermination camps. Innocent people were packed into cattle wagons, often with little food or water, and scarcely enough air to breathe.

For the Reichsbahn, it was a booming business - it was paid for each adult and child it transported to the extermination camps.

Adult prisoners and children over four were charged a fare - four pfennigs per km for adults, two pfennigs for children - earning the railway millions of marks.

From 1941, trainloads of 400 or more people, which amounted to huge overcrowding, received a 50% discount.

'Feeling responsibility'

Deutsche Bahn said the tracks and freight of the Reichsbahn were integral to the Nazis' extermination plan.

"Without the Reichsbahn, the industrial murder of millions of people would not have been possible," said Susanne Kill, a Deutsche Bahn historian.

"It is late, but it is never too late to remember. I am pleased that we have this exhibition in such a prominent place," said Hermann Simon, the director of Berlin's Centrum Judaicum.

"Deutsche Bahn knows that it played a big and bad role in the Holocaust, but it took a long time for it to acknowledge that.

"But at least now the rail operator feels responsibility for what happened in the past," Mr Simon added.

After Berlin, the exhibition is moving to other German stations, including Frankfurt, Halle, Muenster and Munich.