Five minutes walk north from the Pancake Rocks walkway is the Punakaiki Cavern, hidden away on the eastern side of the main road. Car parking is available on the sea-side of the road, slightly north of the cavern. Take care when crossing the road.
A very short walk from the main road leads to the stairs up to the cavern entrance. The Punakaiki Cavern is a Karst cave, formed with a combination of water and carbon dioxide, carving out the cave from the Oligocene limestone.

Make sure you take a torch to explore the cavern and wear suitable footwear.

The cavern features glow worms, the larvae of a large mosquito-like fly. In order to survive they build traps consisting of vertical hanging threads of silk. The silk thread is studded with sticky droplets of mucous to catch small insects (mosquitoes, midges, fruit-fly, etc.) that are attracted by the light. In actual fact they are not worms at all.

There are also stalactites in the cavern, formed when calcium carbonate and other minerals, drip from the cavern ceiling over time, eventually creating hanging formations tapering down to pointed tips, resembling solid cones.