At River Landing Park, a major culture flourished more than 1,000 years ago and built a complex of at least seven platform mounds, including the largest earthwork at the site. Construction began nearly 2,000 years ago during the Swift Creek era by prehistoric Native Americans with skills in engineering, design, and astronomy who were part of a massive ceremonial complex at the Kolomoki Mound near Blakely, Georgia. Other builders may have finished the mounds during the Mississippian era (A.D. 900-1450), called the Fort Walton time in this part of Florida. Preliminary research shows the mounds were aligned to the winter solstice and other astronomical events and functioned as a giant calendar. Important leaders lived atop the mounds, and village areas and fields of corn, melons, and other crops surrounded the complex. Hunting, gathering edible nuts, fruit, and plants from the floodplain forests, and fishing in the Apalachicola River supported the inhabitants. The site owed its existence to the river and its tributaries, the Chattahoochee and Flint, whose trade routes extended from the Gulf of Mexico far into the mountains of North Georgia. Located just below the confluence where the Chattahoochee and Flint merge to form the Apalachicola, the Chattahoochee Landing site was a major center for trade and commerce. The mound known as Mound B, the Great Platform Mound, has two flat areas on top, one slightly higher than the other, which likely served as building sites for the home of the village's principal chief or for a temple structure. The mounds are sacred to the descendants of those who built them and have survived for more than 1,000 years.