I have been there several times, and to this day when you run your hands through the sand you still come up with metal fragments. Until you see it you can't imagine the number of bunkers, tunnels, defensive positions the Marines had to defeat. It is incredible.
I'm glad Eastwood got permission to film there (seem to remember that it was no easy task). Authenticity adds so much to a movie.
Last month I visited a relative who traveled to Iwo Jima about 10 years ago. He passed on to me some back sand and a relay from General Kuribayashi’s communication center. With the restricted access, the bunkers and much of the stuff in it's still as we left it 60 years ago.