Sidrón Cave

The Sidrón Cave is a non-carboniferous limestone karst cave system located in the Piloña municipality of Asturias, northwestern Spain, where Paleolithic rock art and the fossils of more than a dozen Neanderthals were found. Declared a "Partial Natural Reserve" in 1995, the site also serves as a retreat for five species of bats and is the place of discovery of two species of Coleoptera.

Source: Wikipedia