Sandy Creek Park is Athens' big outdoor release valve, wrapped around Lake Chapman north of town. It has trails, picnic areas, disc golf, boat access, and enough space that it feels different from the college-town streets and music venues that usually define Athens.
It is most useful for travellers with children, dogs, or a free half-day when the weather is good. Do not expect wilderness, but do expect a practical local park where you can walk under trees, look over the water, and see how Athenians spend an ordinary weekend outside.