Subterranean waterfall

A subterranean 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 Vrtoglavica Cave in Slovenia, and is at least 400 metres (1,300 ft). A renowned example in the United States is Ruby Falls, 44 metres (144 ft) high, in Lookout Mountain Caverns, a show cave in Tennessee.

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