Between 1941 & 1945, the most notorious concentration camp for the Nazi's was here.
Auschwitz actually has two parts: Auschwitz I, in the village of Oświęcim, and Auschwitz II, or Birkenau. Auschwitz I is where there are indoor museum exhibits in all the former prison buildings. Auschwitz II, or Birkenau, has no museums, it is just the concentration camp (or what remains).
Before WWII this camp was a base for the Polish army - that explains why it was here and why Hitler didn't have to build it, he just took it over. In 1942 it became a death camp. At the time of liberation, at least 1.1 million people had been murdered here (960,000 of those were Jews).
The saying below "Arbeit Macht Frei" translates into Work Sets you Free. Check out the letter B and how it was welded on upside down. It was welded on by inmates, exercising their own rebellion about what was happening to them!
Above are just some of the buildings. Each building has