Our journey starts millions of years ago, before Spain and Europe as we know it existed. This land used to be submerged deep underwater. Over time, minerals and salts were transformed into sedimentary rock. Travertine, limestone, and marble descend from the same components and represent various phases of calcification. On the top, travertine is the most porous and pitted. Dig a little deeper and you'll find limestone. Deeper still, is marble, which is the most prized and valuable. It takes about 250 million years to form marble.