Sweetwater Creek State Park is located close to Atlanta and the mill pictured above was featured on the film Hunger Games: Mockingjay Part 1. There are 15 miles of hiking trails here and my favorite is the moderate yellow loop (3 miles). Fees: 5$ parking for day use or 50$ annual park pass available for all state parks.
https://gastateparks.org/sites/default/files/parks/pdf/trailmaps/SweetwaterCreek_TrailMap.pdf
Address: 1750 Mount Vernon Road, Lithia Springs, GA 30122