I'm sure everyone remembers where they were when the news came though of the first plane crashing into the first tower, and how we all felt. I often think about what the world was like before 9/11 - as I do a lot of air travel and security requirements have changed significantly.
For me, the visit to the 9/11 memorial site was really important, as it made me more aware of the event itself, the sheer number of people who lost their lives, and the changes that we have had to make to our every-day lives to accommodate terrorism.
It is difficult to provide a description of the site as my view will be different to others, as everyone goes into the site with a different emotional thought. So it is best to leave it you, to absorb the moment and reflect.