The Moeraki Boulders

Scattered along a quiet beach on the Otago coast are dozens of almost perfectly round stone spheres, some of them taller than a person, half-buried in the sand at the tide line. The Moeraki Boulders look man-made, or dropped from space, and they are neither.

They are concretions, formed over millions of years as minerals built up layer by layer around a core, like a pearl growing in slow motion underground. The sea has spent the last few million years wearing away the soft cliffs behind and rolling them out onto the beach, where they now sit in clusters, grey, cracked and strangely deliberate-looking.

Up close the cracked ones are the best. Their smooth shells split open to reveal honeycombed interiors veined with pale crystal, so they look less like rocks and more like giant fossilised eggs. We arrived around lunchtime, walked the beach, and spent far longer than planned just wandering between them, peering into the broken ones and running our hands over the smooth ones.

It is a quick stop and an easy one, right off the main road, and it is genuinely odd in the best way, one of those places that makes you tilt your head and ask how on earth nature managed this. They are at their most photogenic at sunrise or sunset, when the wet sand mirrors the sky, but they are worth a look at any hour.

Do not make a special pilgrimage, but do not drive past either. Half an hour among the Moeraki Boulders is half an hour well spent.