A subterranean waterfall, tierous waterfall, or underground waterfall is a waterfall located underground, usually in a cave or mine. They are a common feature in cave systems where there are vertical or near vertical geological structures for the weathering process to exploit, and sufficient gradient between the sink and the rising. The highest known subterranean waterfall is in the Vrtoglavica Cave in Slovenia, with at least 400 metres (1,300 ft).

Media related to Subterranean waterfalls at Wikimedia Commons