"Sink Hole Capital of the U.S.A." The most dominant land form in this area is the sink hole. These "holes" can be seen in and around Fountain, many have been filled or modified in size and shape. Sink holes, caves and caverns form in the limestone bedrock that lies immediately beneath the fertile soil. A sink hole can be viewed at the entrance to the city of Fountain (Hwy. 52) near the welcome sign. There is also a viewing platform near the Root River Trail Head.