The Cambrian fossils of Fontanarejo Nature · Fontanarejo, Montes de Ciudad Real, Ciudad Real Image of Fontanarejo, not of the place itself. Outcrops of Cambrian rock some 530 million years old containing fossils of primitive sponges. The Geological and Mining Institute of Spain has catalogued them as a Point of Geological Interest. Photo: Ramón Peco (CC BY-SA 2.0) What to see and do in Fontanarejo