Devil's Millhopper Geological State Park is fascinating and worth a visit to see the 120-foot-deep sinkhole that exposes over 100 feet of rock layers. A miniature rainforest is inside the sinkhole, with streams that trickle down the limestone year-round with lots of diverse plant life. You can enter the sinkhole via a boardwalk and observation deck and learn about the fossils in the sinkhole, including shark teeth, shells and the fossilized remains of extinct land animals.