Cave paintings are paintings found on cave walls and ceilings, and especially refer to those of prehistoric origin. The earliest such art in Europe dates back to the Aurignacian period, approximately 40,000 years ago, and is found in the El Castillo cave in Cantabria, Spain. The exact purpose of the paleolithic cave paintings is not known. Evidence suggests that they were not merely decorations of living areas, since the caves in which they have been found do not have signs of ongoing habitation. They are also often located in areas of caves that are not easily accessible. Some theories hold that cave paintings may have been a way of communicating with others, while other theories ascribe a religious or ceremonial purpose to them.