Millstone quarries are the sites where hard and abrasive stones were extracted to be fashioned into the querns or millstones to grind flour for bread, the staple food of our ancestors. These stones equipped the different grinding mechanisms, from the Prehistoric hand-driven saddle quern to the sophisticated industrial mills driven by wind and water. These little known extraction sites, ubiquitous throughout the European landscape, have been largely neglected. This study, focusing on the southern half of the Iberian Peninsula, attempts to draw attention to these often spectacular sites that merge so well with nature.