Any indication whether they sit on private or public land?
The Georgia Guidestones, Elberton’s most unusual set of granite monoliths, poses a mystery for the numerous visitors who visit the site seven miles north of Elberton on Georgia Highway 77. Known as America’s Stonehenge, this 19-foot high monument displays a 10-part message espousing the conservation of mankind and future generations in 12 languages. The Guidestones also serve as an astronomical calendar, and every day at noon the sun shines through a narrow hole in the structure and illuminates the day’s date on an engraving. The names of four ancient languages are inscribed on the sides near the top: Babylonian cuneiform, Classical Greek, Sanskrit, and Egyptian Hieroglyphics. The Guidestones are mysterious in origin, for no one knows the identity of a group of sponsors who provided its specifications.
https://www.exploregeorgia.org/elberton/general/historic-sites-trails-tours/georgia-guidestones