You are first greeted by the famous quote by Pastor Martin Niemoeller(also, this link when clicked provides a chronology of the holocaust):
First they came for the Communists, but I was not a Communist so I did not speak out.
Then they came for the Socialists and the Trade Unionists, but I was neither, so I did not speak out.
Then they came for the Jews, but I was not a Jew so I did not speak out.
And when they came for me, there was no one left to speak out for me.
Here's a black and white photo essay.
It is a powerful memorial that accurately depicts the enormity of the mass murder. Much more however, you are reminded how important it is to value and defend life. If you're ever in Boston, I highly recommend that you check it out.