The headland at Mautohe Cathedral Cove is not rock in any durable sense. It is ignimbrite, volcanic ash thrown out some eight million years ago and welded into soft white stone, and the sea has been taking it apart ever since. The arch is one stage of that work. The passage runs clean through the headland on the Coromandel peninsula of New Zealand's North Island, high enough overhead to feel like a nave. It takes you a dozen steps out of shadow into pure glare, with the noise of the surf doubling under the ceiling. Behind you is broad Mares Leg Cove; ahead, a pocket of sand pinned under the cliffs. Te Hoho stands off it, a white stack of pumice breccia pinched almost through at the waist and crowned with a tuft of pōhutukawa. Coming in from Hahei by kayak instead gets you the rest of the evidence: stacks, blowholes and sea caves cut into the same crumbling ash the whole way along the coast.
That softness has a cost on land. Storms closed the clifftop track for two years from 2023, and through all of it the boats out of Hahei kept the cove open from the sea. A side track off the clifftop route climbs to the Tokawhakairo lookout, twenty-five minutes return, where the pōhutukawa part on the bay and its islands. Ngāti Hei trace the bay's name to Hei, who came ashore from the Te Arawa canoe and claimed this coast for his descendants; the cove's own name is Mautohe. In 2007 a film crew borrowed the arch as a door to Narnia, the curve of a London Underground tunnel dissolving into the curve of the stone. One thing here is going the other way. The shallows under the arch have been closed to all taking since 1992, the country's sixth marine reserve. The sea is warmest in February and March, weeks after the summer crowds thin, and the snapper you swim out over are the fat, unbothered kind you almost never meet from a beach.