We visited the Flight 93 Memorial recently. It’s not that long of a drive from the DC area. The Memorial is still a work in progress, but it is nothing short of powerful already.
The wall follows the flight path, which leads your gaze to the impact site. Each person’s name is engraved on a different wall panel. Only family members are allowed out to the impact site.
There are small grooves cut into the barrier every so often where people have laid mementos. You can see the impact site behind the barrier in one of the photos above.
In a small building there is a bulletin board where you can pin your thoughts.