There are also granite memorials to the 9/11 first responders, a little church, a pentagon-shaped gazebo, and all kinds other remembrances and memorials to that day.
They obtained actual steel beams from the World Trade Center, a large limestone block from the Pentagon, and an urn of soil from the Flight 93 crash site in Pennsylvania. There were some dedicated people who built this tribute to arguably the most horrifying event in America's history.