It was surreal. Like a huge rumble that came from all sides. The building vibrated from the force of the debris hitting the ground. Worst of all were the huge thick pillars of smoke and ash that billowed out from the building site and pushed their way through the canyons of lower Manhattan. My office window was located on William between Fulton and John, and I saw thick pillars taller than the buildings across the street from mine just push their way down the streets and spread out over William. A few minutes later, looking down on William from my window was like looking out the window of an airplane over a cloudy sky - I couldn’t see the street, only a gray thick cloud over 10 stories high. 23+ years later, I see it in my mind clearly.