Remember

12 years ago the Towers were needlessly destroyed and the world changed.

There was an account of someone who had witnessed the offense from Lower Manhattan that day.   It was an email that got passed around the world many times.   Reproduced on Neil deGrasse Tyson's web page, I have the link here. 

The current use of the site is for the National September 11th Memorial Museum.  You can see the write up on Wikipedia here.   The picture below is from that page.