Since you're making it part of a larger journey...
Consider a tour of Haunted Houses of the South! Plenty of those in Savannah, for a start! And there's the Georgia Guidestones for your dose of Southern-fried Stonehenge!
Beautiful landscape, great hunting, great fishing, outstanding variety fine foods and oooh those beautiful Georgia peaches. I mean the two legged kind! Just to name a few reasons to visit out great state.
If you are up for a challenge, you might try to find the Boarding House and have a great family style lunch. Otherwise, Lada Thai has surprisingly great Thai food for the middle of Georgia!
North Georgia mountains are always great especially in the fall. Someone mentioned the Georgia Aquarium which is a great reason. I've been to Sea World which is really cool, but the Georgia Aquarium is a totally different experience, I believe it is the largest indoor aquairium if i'm not mistaken.
Come to visit for, the great people, great shopping, beautiful scenery, museum's, historical sites, the aquarium, the World of Coke, and the GREAT FOOD!
Others have covered the beauty of the State .. let me tempt you with craft beer ...
The Brick Store, Leons and Twins in Decatur
The Porter in Little Five Points
The Trappeze in Athens
The Distillery, Crystal Beer Parlor and Moon River in Savannah
plus many many more ...