Whenever I visit Washington D.C. I try to find time to go to Arlington Cemetery. I don't visit the famous graves. Instead I trudge along the main road to a point at the far corner overlooking the Pentagon, which is where my father is buried. Well, in-urned, actually, since he was not important enough for an actual burial. In the military, you carry your rank with you to the grave, literally.
It so happens that I pass by the grave of Grace Hopper on the way to the columbarium, and I always stop and pay my respects.
Arlington is nothing if not military. All of the headstones are identical (with a few famous exceptions), and no decoration is allowed. There are particular occasions on which you can leave flowers or flags (like Memorial Day), but the rest of the time it's just green grass and white headstones. So people have a habit of marking their presence by placing a small stone on top of the headstone. I find it to be very touching, a tiny bit of civil disobedience. I don't think I have ever been to Grace's grave when there wasn't a stone on it. To me it's a great reminder that others also visit her and care. So here is her current stone. And if you visit, please clean the bird crap off her headstone, and add a pebble if you can find one. (She's located at 59-973)