artifacts, though no rock art. El Soplao The Cave of El Soplao is located in the municipalities of Rionansa, Valdáliga and Herrerías. It is admired worldwide for the quality and quantity of geological formations or speleothems contained in its 17 miles in length, although only 6 are open to the public. There are rare formations as helictites (eccentric stalactites defying gravity) and "draperies" (sheets or translucent banners hanging from the ceiling). Its formation dates back to the Mesozoic, in particular the Cretaceous period 240 million years ago. Torca del Carlista Torca del Carlista is located in Cantabria, and contains the fifth-largest underground chamber in the world. Del Valle The Cave del Valle is located in the municipality of Rasines and also known by locals as "La Viejarrona." It has a majestic entry from which the Silent River springs, a tributary of Ruahermosa, both of Assos. It is an important site, both prehistorically as well as speleologically; it dates to about the Azilian and Upper Magdalenian. Chronology of discoveries See also Art of the Upper Paleolithic List of Stone Age art References External links Human Timeline (Interactive) – Smithsonian, National Museum of Natural History (August 2016). Archaeological sites in Spain Bien de Interés Cultural landmarks in Cantabria Limestone caves Prehistoric sites in Spain Show caves in Spain Stone Age Europe