I was in college when those buildings were erected. We were on the west side of the river. Everyday, as students we would look to see the progress of the construction. A few years later when the structures were complete and the work moved to the interior, I used to walk through the unfinished lower level after arriving in "the city" by train.
I even worked at a job where we sold equipment that was installed in the towers. We used to fly down the river below the level of the observation deck (completely legal and safe BTW before anyone asks) and sightseers would wave to the planes.
It was simply unbelievable to see the twin towers come down. I was nowhere in the area at the time of the attack (about 40 miles away).
It was plainly visable from the campus of my alma mater, and the students at the time were understandably horrified.
I still can't believe that they're gone!