Further up the coast, near the fishing village of Moeraki, are the famous Moeraki boulders. Strewn like giant marbles across the sand of Hampden Beach, the spherical boulders are not in fact the product of erosion but of a natural chemical process. They were formed some 60 million years ago by the gradual accumulation of lime salts around a central lime crystal core. These septarian concretions, as geologists prefer to call them, gradually appear from the cliffs behind the beach as the soft mudstone in which they are embedded is eroded away by the sea. Some of the concretions are over 13ft (4m) in circumference and weigh several tons. In a strategic position near the boulders is a large, reasonably priced restaurant with excellent views over the sea.