While I was in Berlin, I went to see the East side gallery which was a gallery of paintings by people from different countries on a part of the Berlin wall that was preserved. This part of the wall was preserved so that the future generations can see and learn from the history so that it doesn't repeat. It's about a 2 KM wall with beautiful murals that talk about world peace and other message-oriented stuff. We went there during the afternoon when it wasn't too crowded. There is a bus that goes there and you can walk to the other end of the wall.
Points of interest
East Side Gallery (Berlin)
Part of the Berlin wall that was preserved and converted into a mural gallery.