Not to "air burst" anyone's bubble, but I believe it is a lamp. It was meant to be recessed into the sidewalk, flush with the pavement. They use them to illuminate signs, curbs and such. Notice the 4 nuts on the cap. The center ring that looks like a primer is actually the lamp lense cover. It looks as if there is a wire towards the center, between the metal braces with the holes. I'm not much of a betting man, but I'd say someone ran over it and it got crushed below the surface of the pavement. Then someone dragged it back out hoping to at least salvage it shining some light still. Just my observation.