The Blowhole Cliffs at Piha
The access to the Blowhole Cliffs at Piha are little known. There is a rough track through young pohutukawa trees that goes above the Blowhole tunnel. From there, you can reach the top of the cliffs that overlook an unnamed beach. The beach looks enticing, but to get there, you would need to wade/swim/walk through the tunnel at low tide.
The track comes out onto the cliff at the north end. Look closely and there is a side track that takes you to a much more open area with a better view of the beach and bay. The rock formations on either side of the beach are photogenic and there is a patch of grass perfect for a picnic.
The cliffs are quite crumbly, so take the advice on the Auckland City boards and be extra careful near the edge.