Karst refers to terrain largely drained by subsurface conduits and caves. Karst landscapes are characterized by surface features such as springs, sinkholes, shallow depressions, and rolling hills. Karst regions are also known for their subsurface or below-ground features such as conduits and caves. What makes a karst region unique is the way runoff drains from the land. In karst regions, some of the runoff flows into surface features such as sinkholes where it then travels underground. Some of this infiltrated water re-emerges at springs, and some continues moving underground.