Buckhead is the north side of Atlanta while the airport is south of the city. The airport is in Hapeville and there’s not much there either unless you’d like to visit the original Chick-Fil-A location or pay a lot of money to drive a Porsche at their facility next to the airport.
Buckhead’s known as the ritzy area but also isn’t too much. The Atlanta History Center is located there and it is a nice museum on a large campus that includes a few different buildings, the main one being The Swan House (aka Cornelius Snow’s mansion in The Hunger Games movies).
Honestly, I’d second the Georgia Aquarium and Centennial Olympic Park as a recommendation if you like aquariums. The MARTA rail line runs between the airport and Alpharetta so you could take advantage. From there you could also take the Atlanta Streetcar (or walk if you feel comfortable doing so) over to Sweet Auburn. Hit up the Sweet Auburn Market (Municipal Market) which has a variety of food stalls inside and then make your way over towards Ebenezer Baptist Church and the King Center. Downtown hasn’t seen the investment of midtown, so it has more blighted areas, but it’s always captivated me. If you like old cemeteries, Oakland Park isn’t far south from the King Center and there’s a nearby MARTA rail station (although access is a bit inconvenient).
