Welcome to Devil's Millhopper Geological State Park In the midst of north Florida's sandy terrain and pine forests, a bowl-shaped cavity 120 feet deep leads down to a miniature rain forest. Small streams trickle down the steep slopes of the limestone sinkhole, disappearing through crevices in the ground. Lush vegetation thrives in the shade of the walls even in dry summers. A significant geological formation, Devil's Millhopper is a National Natural Landmark that has been visited by the curious since the early 1880s. Researchers have learned a great deal about Florida's natural history by studying fossil shark teeth, marine shells and the fossilized remains of extinct land animals found in the sink. Visitors can enjoy picnicking and learn more about this sinkhole through interpretive displays.