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