On a recent December morning, Mack Jones hiked a trail bordering the lake at Sandy Creek Park in Athens before he ventured off the path and up a forested ridge. There he showed a group following him a series of mysterious stone terrace walls and rock piles. "It's hidden in plain sight, and it's been that way for the 30 years the park has been here," Jones said. "No one has messed with it and maybe they won't." Jones believes those numerous rock piles - and especially the stone wall terraces lacing the hillside - might constitute evidence that the...