Cathedral Cove earned Department of Conservation protection in 1976, seven years after a single access track was cut through coastal pōhutukawa forest to link Hahei Beach with the white-sand pocket beneath Te Whanganui-A-Hei's limestone headland. The natural arch — fifty metres wide, carved by millennia of storm surge — frames a marine reserve where blue mao mao and snapper glide over volcanic reef visible through water that holds eighteen degrees year-round. The cove sits two and a half hours east of Auckland by road, threading State Highway 25 past Thames, Tairua, and the Coromandel Range's kauri remnants before dropping into Hahei. Geologists date the surrounding cliffs to the Whitianga Group rhyolite, erupted eight million years ago during the Miocene and shaped by wave action into the keyhole profile that defines the Marine Reserve's southern boundary. Pōhutukawa roots anchor the clifftop trail, while kōwhai and karaka shade the descent to sand compacted fine enough to hold boot prints at low tide. The arch itself — calcium-poor ignimbrite, susceptible to salt weathering — loses an estimated two millimetres of surface annually, a rate measured by the University of Waikato's coastal geomorphology unit in 2019. Coromandel Peninsula day trips from Auckland bundle Cathedral Cove with Hot Water Beach, twelve kilometres south, where geothermal springs vent through sand at forty-five degrees Celsius during the two-hour window either side of low tide. Tour operators depart Auckland's waterfront between six and seven each morning, crossing the Firth of Thames before the Bombay Hills climb. Return journeys typically reach the city by eight in the evening. The Marine Reserve, gazetted in 1992, prohibits fishing and anchoring across eight hundred forty hectares of subtidal reef; kayak operators launch from Hahei Beach under permits issued annually by DOC's Waikato Conservancy. Visitor numbers peaked at three hundred twenty thousand in 2019, prompting track closures for sediment control and root protection. The Grange Road carpark — two kilometres inland from the arch — holds sixty vehicles; overflow parking opens during December and January. Cathedral Cove remains one of the North Island's most photographed landforms, its arch appearing in promotional material for New Zealand tourism since the early 1980s and in the 2008 film *The Chronicles of Narnia: Prince Caspian*, which shot beach sequences over eleven days in April 2007.