The Moeraki Boulders are amazing stone spheres and they remind me a lot on those mysterious spheres which can be found in South America or some European countries.
Unlike the mysterious spheres from South America for which archaeologists do not have reasonable explanation, those are something different. Those spherical boulders are formed in sea floor sediments in the process which is similar to process of the creation of pearls.
Those spheres were forming for thousands of years and it is amazing how their shapes are almost perfect like they were made by humans not by the nature. Some of them are pretty big and are about 3 meters in diameter. Those boulders can be found on a Koekohe Beach in New Zealand.