I feel it should be mandatory for everyone on Earth to visit, as a lesson on "Pay attention what's happening in your home country, don't let this happen again."

Do allow more time than you think. I took an early morning train out and late afternoon train back. The inmates were taken there by train. It is so comforting to know that, unlike them, you have a train ticket to leave.

Start at the small camp, there is a movie, pick up a guidebook with a map. Tour the barracks, the exhibits inside will move you. The one that got me was the shoes. . .

But Birkenau. . .none of my pre-trip reading really explained the one thing you have to experience: the size of the place.