Karst

a karst landscape is one created in a limestone area and which occurs due to the limestone itself. The distinctive landforms are a result of solutions moving through joints and fissures in the rock dissolving the rock, enlarging cracks and joints and creating underground waterways and caves. Features typical of a karst include networks of furrows and sharp crests, funnel-shaped hollows and eventually conical hills and steep-sided depressions of impressive scale.

Taken from Dictionary of Science