This National Recreation Area is located in Sulphur, Oklahoma...south of Oklahoma City. The place is a popular getaway from the summer heat with swimming holes and grill sites. There are several nature hikes and the Lake of the Arbuckles is a popular swimming / boating location.
Pro Tip: There is a herd of fenced in bison you can view but the park signage is not updated with the current location of the herd. If this is a must see, avoid hiking trails that lead to empty pastures and ask the Park Rangers at the visitor center for detailed navigation instructions.