The Tear Drop Monument was donated by the Russian people in tribute to those lost on 9/11. The names of those lost are inscribed in the base similar to the Vietnam Wall in DC. The walkway is lined with stones donated by those in remembrance of this day. The site is directly across from the Statue of Liberty, and looking at that skyline, you truly do see what's missing.
The third plane came in low over the Arlington National Cemetery and struck the western face of the Pentagon, penetrating through three of the building's five rings. All 64 people on the plane, including the five hijackers, were killed; 125 in the Pentagon also died.