Cerro del Hierro

The Cerro del Hierro Natural Monument is located halfway between the towns of Constantina and San Nicolás del Puerto, in the Sierra Norte de Sevilla Nature Reserve. The presence of iron in the rocks in the hill led to mining activity in this area which was a feature from Roman times until the last century. This activity left a landscape of unique shapes and colours, featuring needles, corridors, karstic fields and sink-holes, caves, chasms, travertines and limestone pavements. The extraordinary beauty comes from the limestone rocks which have been partially eroded by rainwater and snow, giving rise to this spectacular karstic formation of which climbers are so fond. -- from andalucia.org