Where is the World Trade Center? asks the tourist.

It was destroyed in 2001 with the loss of nearly 3000 lives is my answer.

I recently moved my office from midtown to the World Financial Center. I worked for another company with offices at 22 Cortlandt Street, next to the World Trade Center on 9/11/2001.

Everyday I walk past the area where so many were killed and when there is even today no memorial to this attack on the United States and to the people who died there on that day.
video tour

As soon as I leave the secured area of my company, I'm in a lobby full of tourists and as I walk around lower Manhattan there are few signs and landmarks that point to the location of the site of the World Trade Center, so I'm helpful in pointing out how to get to the corner of Church and Vesey Streets.
Google Satellite Photo

The 4th anniversary this year falls on a Sunday so it is certain to be low-key.

Number 7 World Trade Center burned to the ground. This held the city's emergency command center. The mobile command center to which they fled later had to be abandoned as well.

Number 7 is already being rebuilt. The outside covering facade is being installed this week.