One of the most moving memorials to the Holocaust, for me, is in Berlin. It has the rather memorable name of Memorial to the Murdered Jews of Europe. I first saw it when I was 16, travelling Eastern Europe as a student ambassador with People to People. I can remember walking through the maze of stone and having the feeling of utter isolation. Going back nearly 6 years later, I had much the same feeling of isolation and hopelessness.
If you’re in Berlin, I would defo check out the memorial. It’s located just about a block off of the Brandenburger Tor (Brandenburg Gate). It’s free to walk around and experience the memorial on your own.