When you find this 1,160-acre retreat along the Olentangy River in Southern Delaware County, you find serenity. (Not that it's hard to find, what with its main entrance right on, essentially, High Street.) Hike, jog, walk your dog, picnic. It's a perfect way to spend a morning/afternoon/evening.
Runners-up:Scioto Audubon Metro Park, Alum Creek State Park