A subterranean waterfall or underground waterfall is a
waterfall
A waterfall is a point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf.
Waterfalls can be formed in several ...
located underground, usually in a
cave
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...
or
mine.
[Vrtoglavica Cave
Vrtiglavica, also Vrtoglavica (both from Slovene ''vrtoglavica'' 'vertigo'), is a karst shaft on the Kanin Plateau, part of the Kanin Mountains, Western Julian Alps, on the Slovene side of the border between Slovenia and Italy. It has the de ...]
, and is at least . A renowned example in the
.