These unusual boulders on the beach are about forty miles north of Dunedin. There are similar ones in various parts of New Zealand, but at up to 2 metres across, these are the biggest. Obviously a huge tourist attraction, even visiting on Christmas Day I had to get low and use the rock in the foreground to hide a large group of tourists. The rocks are hollow and made from mud, fine silt and clay, cemented by calcite. Scientists estimate the age of the larger boulders at 6 millions years old.