The drive through Manawatū on State Highway 1 is quite spectacular. About halfway between Taihape and Mangaweka, the road roughly tracks the meandering Rangitīkei River, which has carved a channel through the massive, blue-grey-white mudstone, resulting in a series of high cliffs. With a visit to Whitecliffs Boulders you can experience both the cliffs closer up and see a North Island variation on the Moeraki Boulders.
Continue south of Mangaweka for about 10 km or so, then turn east onto Otara Road and take the bridge over the river. Shortly after, you will come to Peka Road. This is very rural and feels like nowhere, but keep going to the very end, including a steep hill climb, a farm gate, then a steep rough downhill to a carpark.
From the park it’s about a 20 minute walk to the boulders. Although the boulders are the highlight, the walk is superb; follow the orange markers across farm paddocks high above the river, with a steep drop down to the river below the main series of cliffs. Note there is no shelter on the walk so I would avoid a very hot day or especially bad weather. There is a also a small honesty box fee so try to remember to take a bit of cash.
The Boulders themselves are magical, even wondrous experience; a large number of mostly big round boulders in a small forest, covered in bright green moss and, in some cases, tree roots.
The Boulders are geologically the same kind of thing as the ones in Moeraki. The main differences are the quantity of the boulders, with more at Whitecliffs, and the environment. Whereas Moeraki Boulders are borne from coastal cliffs and tumble onto the beach, Whitecliffs Boulders have come from the cliffs carved out by the Rangitīkei River and ended up in a section of moderately swampy rainforest.
Like Moeraki, the Whitecliff Boulders are spherical ball concretions made from mudstone. It is believed that organic material buried millions of years ago creates a node around which natural forming cements can aggregate and solidify. The cement in this case is calcium carbonate.