Sadly there is little evidence of the pa today and a violent storm in 1976 destroyed the spindly, angled rock outcrop that resembled the hind leg of a horse.
As I sit and contemplate the scene, gentle waves are swishing over the sand in ever-increasing tongues of water that reach into the cavern, threatening to cut off access.
Imposing rock stacks of the same pink-tinged ignimbrite rock stand defiantly out in the bay, like sentinels in the turquoise sea. Te Hoho Rock is a delicately sculptured pinnacle of sandstone resembling the prow of an ocean liner steaming into the beach.
I've come to Cathedral Cove on a Sea Cave Adventure with Dan Saward of Whitianga Adventures in a purpose-built rigid inflatable boat.
Our journey of exploration has brought us from Whitianga Wharf past Ferry Landing, the oldest stone jetty in Australasia, Flaxmill Bay and the massive limestone bluffs of the Shakespeare Cliff Scenic Reserve.
Captain Cook named Shakespeare Cliff after the famous playwright as he fancied that he saw a profile of his face in the angular rock.
Locals claim that the rocky outcrop, which is a blend of volcanic ash and pumice from an eruption of seven million years ago, resembles an Indian chief's head.
Beyond the cliffs is Cooks Beach, a long cream swathe of sand where the great navigator observed the transit of Mercury across the sun and celebrated the event with a formal ceremony to declare New Zealand a possession of King George III.
He met the Ngati Hei people on the beach and they led him to the pretty Purangi Stream, where he replenished his water supplies.
Cooks Beach is one of those idyllic seaside resorts that keep alive the great tradition of summer holidays at the beach for Kiwi families. Long, hot summers filled with the joyous sounds of children playing in the sun and balmy evenings gathered around the barbecue.
We cruise slowly past Cooks Beach, Stingray Bay and Gemstone Bay to reach Hahei Beach.
Here, we admire the breathtakingly beautiful crescent of white sand, backed by gnarled, overhanging pohutukawa trees, a motor camp and private homes.
Maori named the bay Te Whanganui a Hei, after Hei, the chief of the Te Arawa canoe that arrived here around 1350.
Our family has enjoyed many summer holidays at Hahei, lazing on its sweeping crescent of brilliantly-white sand and snorkelling around its sheltering islands.
This little settlement began as the Harsant's farm with a few campsites on the foreshore. Today the bay is bustling with holidaymakers. It's a perfect slice of Kiwi beach holiday culture.
After a short run down the coast we arrive at a long curving beach of honey-coloured sand where a group of young board-riders are braving the breaking waves at a surf school. Further up the beach a knot of people are getting into hot water.
The scene is reminiscent of a beach carnival 'Big Dig' treasure hunt or sandcastle building competition. This is the uniquely Kiwi do-it-yourself spirit in action. Families and couples are digging their own private spa pools as hot mineral water bubbles up through the sparkling sands.
The charming beachside settlement of Hot Water Beach offers these natural spa facilities two hours either side of low tide every day. The challenge is to time your excavations right so that you capture an ideal mix of cool salt water and hot mineral water.
More of Coromandel's hidden gems await as we motor down the coast from Hahei.
Every rocky bay and sandy cove is beautiful. Stunning geological formations rise up from the sea as a testament to the power of volcanic eruptions and the creative work of natural erosion.
Seabirds circle above the honeycombed cliffs and little swifts duck into holes only to emerge seconds later to swoop down to the water to chase unwary insects.
We nose carefully into Orua Cave and test the amazing acoustics when we raise our voices in song. Above our heads is a circular opening that reveals the blue sky. Below, are massed schools of blue maomao surging to and fro in the still, silent sea. They are congregating in this sound shell of a cave to escape hungry predators in the open ocean.
The Coromandel Peninsula is blessed with many natural hideaways and the Mercury Bay and Hahei coastlines have more than their fair share.
It's a part of Auckland's eastern playground where you can relax, revitalise and unwind, just as the great navigator did two-and-a-half centuries ago.
CHECKLIST
Getting there: Whitianga is 208km from Auckland on the east coast of the Coromandel Peninsula. From Auckland, take Highway 2 through Mangatangi or hug the coast on Highway 25, following the Pacific Coast Highway signs.
The town is the departure point for numerous fishing charter and scenic cruise boats on half-day tours along the coast.
What to do: Whitianga Adventures offers trips exploring Coromandel's coastline.
Further information: See thecoromandel.com or whitianga.co.nz.
