That's not quite right. A funnel-shaped depression of limestone dissolved by rain is called a sinkhole.

A cave is a larger, naturally formed underground chamber that can be accessed from the surface.

Sinkholes often form when rainwater becomes slightly acidic and dissolves the limestone, eventually creating a depression. These depressions can vary in size from small, shallow pits to large, deep craters.

Over time, a network of sinkholes can form a larger underground cavity, which can then evolve into a cave.