The Okefenokee Swamp is a huge peat bog covering much of south Georgia and spilling over a bit into north Florida. It is the source for both the Suwanee River on the west and the St. Marys River on the east. The name "Okefenokee" means land of the trembling earth, because many of the islands in the swamp are large clumps of floating peat.
Winter is the best time to visit the swamp - especially if you don't want to deal with its more onerous inhabitants - bugs and gators. There is the Okefenokee National Wildlife Refuge and the Stephen Foster State Park along with several other attractions to capture your interest.