I was in NY just a few months before 9/11 and went to the trade center to go up to the top floors to check out the view (or whatever floor they allowed you to go to), but the line to go up was too long. We waited in line for a while, but then decided to go do something else, and I specifically remember saying "ah well, we will go up there next time we are here". It made it pretty powerful to see those buildings falling down when you had just been there to see how huge they were.