Mammoth Cave is the longest recorded cave system in the world. The land above the cave system exhibits many karst features, such as sinkholes, emerging underground rivers, and many cave entrances. The park has many miles of trails, including a soon-to-opeMammoth Cave is the longest recorded cave system in the world. The land above the cave system exhibits many karst features, such as sinkholes, emerging underground rivers, and many cave entrances. The park has many miles of trails, including a soon-to-open rail-trail from Park City to the Visitor's Center. Near the Visitor Center is a cemetery for old cave guides.