Cave of El Soplao

El Soplao is a cave in Cantabria, Spain, discovered in 1908 by miners working the La Florida zinc and lead mine. Spanning approximately 27 km in length, it contains the most extensive collection of helictites (gravity-defying eccentric stalactites) ever found, with an average density of around 4,000 formations per square metre. The cave formed roughly 100 million years ago during the Cretaceous period and also contains curtains, cave pearls, and a new mineral form called zaccagnaite-3R. Opened to tourists in 2005, it now draws approximately 300,000 annual visitors.