Its impossible to forget, especially after visiting a place like that. I live a few kilometers from Dachau and it is both a necessary and brutal place to visit. I haven't had the chance to visit Poland, or Auschwitz, but I do have an old whisky bottle from Oświęcim, pre-WW2, which my girlfriend happened upon at a market last year. Before that, I had never thought of a place with such an obvious and dark modern history, having such a rich history before that.