I was in grade school when they started building the Berlin Wall. I remember all us little kids just being astounded that Communists had to have a wall to keep people IN and away from US, LOL.
When it was being built, there was no cleared “no man’s land” yet. The cement blocks were often right against the sides of apt. buildings. People would hang and push off from 2nd story windows to land in the West. Later these buildings were emptied and the windows bricked up. Eventually, the buildings came down.