The limestone and gypsum uplands of the Sierra Baetica, also known as the Cordilleras Béticas (Baetic Mountain Ranges) or Baetic Mountains, stretch from the border with Portugal to the northeast coast of Valencia. The range comprises roughly parallel lines of mountains, the most famous being the Sierra Nevada, and is separated from the central massif and the Sierra Morena by the valley of the Rio Guadalquivir. Natural caves abound in the limestone area and, uniquely, near Sorbas in the gypsum strata. The Sierra Morena is one of the richest areas in the world for metallic minerals, particularly copper and gold, and has been mined since prehistoric times resulting in many mining shafts. To the east of the region, iron, lead and silver have been similarly mined since time immemorial and some mines are being opened to the public, including the gypsum mine at Piulpi that has the largest geode in Europe. Many of the caves have been used as shelters by prehistoric people who left arte de repuestre, cave art, behind. Over 700 caves and rock shelters are so far known in Andalucia, many with public access. This series is a guide to the natural caves and the mines in Andalucia that are open to the public and worthy of a visit for their cave art, formations or industrial heritage.