The Trümmelbach Falls in the Lauterbrunnen Valley in Switzerland are unusual in that, whereas most waterfalls fall off the side of a cliff, these falls tunnel through the rocks on the side of a mountain from a height of 460 feet in a total of ten falls some of which reach heights of 60 feet or more. The Trümmelbach Falls are the largest underground falls in Europe. The source of the water for these falls is snowmelt from the glaciers coming down the Eiger, Monch, and Jungfrau peaks, which rise to more than 13,000 feet above sea level. The water of Trümmelbach Falls has a turquoise color due to glacier debris, and at peak season the stream may carry more than 5,200 gallons of water per second.
The layers of rocks through which the falls flow were laid down as mud rich in calcium carbonate in a shallow sea that covered the area 140 million years ago. Later on, these layers were compressed, turned into stone, and folded as a result of the tectonic uplifting that created the Alps over millions of years. Valleys such as the Lauterbrunnen Valley were sculpted by glaciers some 500,000 years ago. It is believed that during that time the Trümmelbach Falls began forming and acquired their present shape in the last 10,000 years.
In the video below you can see the 7th fall of the Trümmelbach Falls framed by the steep walls of the Lauterbrunnen Valley in the background.
In the next video below you can see the 9th fall of the Trümmelbach Falls. This video reveals the fact that part of the falls are subterranean.