Ok, so we are about 12 miles from the nearest road and find this. Perfect circle about 6' across with a trench around it. Trench is approx a foot wide and about a foot and a half deep. No spillway on the trench, just a circle. Nothing growing on the centre circle except a few weeds, but the structure has been here long enough that moss is growing inside the trench.
After looking around, I found a square steel pin in the centre of the circle (this rules out Ancient Aliens). No markings on the pin, 5/8" square and about 2' long.
http://i123.photobucket.com/albums/o...ps3qhebnve.jpg
http://i123.photobucket.com/albums/o...psd9yyjw7a.jpg
http://i123.photobucket.com/albums/o...psaerdibhq.jpg