The Sierra de las Nieves natural park is located in the hills behind Marbella and to the east of the road to Ronda from the Costa del Sol in Andalucia in Southern Spain. The park centres on La Torrecilla (1919 m) and covers an area of 202 km². This mountainous area has seen little human influence or activity (cultivation) even historically and has a rich variety of flora and fauna. As the name suggests, it can be snow-covered in the winter. The area was studied in the 19th century by Swiss botanist Pierre Edmond Boissier and in 1933 by Luis Ceballos. In 1970 the park was declared a National Hunting Reserve and in 1995 a Biosphere Reserve by UNESCO.
There are a considerable number of large caves in the park, several taking the traditional form of horizontal caverns. Three are of particular interest, namely:
The area is perhaps more famous for its potholes, or simas in Spanish. One of these, GESM, is one of the deepest in Europe. GESM stands for Grupo de Exploraciones Subterráneas de Málaga and was clearly named after the group that mounted an exploration in September 1978. It has still not been fully explored.
The entrance to the pothole is located at 1.670 m and it descends 1.098 m with a few large drops. The Gran Pozo drops 115 m and the Pozo Paco de la Torre has a vertical fall of 194 m. At a depth of 900 m there are some interesting rock formations in the Sala de Maravillas, and Lake Ere is located almost at the bottom.
Sima de la Tinaja is located in the area of the Tajo de la Caina at an altitude of 760 m. It is 54 m deep. It can be reached from Tolox. Many prehistoric artefacts have been recovered from this cave and many are to be found in the Málaga Museum.
Some of the other potholes are mentioned here. The list is by no means exclusive and many are surely yet to be discovered.