Eighteen years now, and I still remember watching the towers come down, watching the TV monitors in the lobby of the nuclear waste remediation firm I was contracting at (engineering design quality assurance) in Columbia, MD. Just surreal, everyone was dead quiet, just staring at the screens. Many people bailed from work early after listening to the clueless talking heads on TV that were doing their best to panic the populace. Finally left work at 5, only to see practically empty expressways, something NEVER seen in the DC-Baltimore area, much less during what should have been rush hour.
Haven't been to the Twin Tower Memorial, but have been to the memorial site outside the Pentagon. The hijackers had a clear shot at the building by descending over Arlington Cemetery, an easy flightpath that no longer exists now that the triple spires of the Air Force Memorial are in place.
184 persons passed at the Pentagon (counting the doomed passengers on Flight 77), but the carnage in Arlington is seldom mentioned in 9/11 coverage. Everything is WTC, other than minor mention of Shanksville, PA, now that that memorial is in place. Typical NooYawk.