Here's how to plan a visit to Georgia's Okefenokee Swamp.Landscape in the Okefenokee National Wildlife Refuge in Georgia.Credit: Alexander Ließ / Getty ImagesSet at the headwaters of the Suwannee and St. Marys rivers in southeastern Georgia, the Okefenokee Swamp is not only one of America’s most important ecosystems, but also the largest blackwater swamp in North America. Its vast stretches are home to several endangered species, like the indigo…