The study of microorganisms involved in the deterioration of prehistoric paintings is of great importance to preserve these singular samples of cultural heritage. This study presents, as an example, results from a research carried out in Altamira Cave (Cantabria, Spain). Altamira Cave contains numerous and well known paintings from the Upper Palaeolithic, dated back around 15,000 years. This work focused in understanding the microorganisms inhabiting this singular system and the potential consequences of its microbial diversity for conservation of these valuable paintings.