I 
  remember the day our transport arrived at Auschwitz-Birkenau. The wagons were 
  opened and the people ordered out. The scenes I observed were just too terrifying 
  to imagine.
  Arek Hersh, survivor.
  
  The Nazis developed a system of camps in order to enforce 
  their rule of terror, first of all in Germany. They repeated this in the other 
  countries of Europe that they occupied. But there were different camps for different 
  functions. The first concentration camp to be built was at Dachau, near Munich, 
  in March 1933. Communists, socialists and trade unionists were put here; anyone 
  who opposed the Nazis.
The 
  infamous gateway to Birkenau. In the later stages of the camps operation, 
  trains passed through here from all over Europe to the ramp, where 
  the deportees were unloaded ready for the selection.