Faith Rogers, an environmental-science intern and volunteer at the Heavener Runestone Park, led me down a cobblestone path toward one of the 55-acre woodland"s biggest attractions – which is also one of the US" biggest historical mysteries. We were deep in the rolling, scrub-forest foothills of the Ouachita Mountains in far eastern Oklahoma, and we were on our way to view a slab of ancient sandstone that still has experts scratching their heads and debating about the eight symbols engraved on its face.