Big Mound City is an exceptionally sophisticated geometric earthwork located about 6 miles east of Lake Okeechobe. The complex possibly served to raise building foundations above the surrounding ground plain which flooded six months of the year. The mounds and causeways in the site are constructed from yellow and white sand.
The large semicircular embankment of the city measures 1,520 feet in diameter. There are 5 circular mounds within the central corral, all measuring approximately 9 feet in height. 8 conical pared mounds are connected to the central mound by radial causeways. The largest of the mounds measures 220 feet in diameter at its base and reaches a height of 25 feet. The walls of the causeway are an astonishing 9 feet high.