The glowworm caves at Te Anau

After a full day on the water we had one more thing booked, and it turned out to be one of the strangest, loveliest hours of the trip. From the lakefront at Te Anau, a boat takes you across the water to a cave system you then explore partly on foot and partly afloat, in the pitch dark. We almost skipped it, tired after a long day, and I am very glad we did not.

You climb into a small flat-bottomed boat and are pulled silently through low, wet limestone passages with the lights off. It is completely black, the kind of dark you almost never experience, and then you look up.

The ceiling is full of stars. Thousands of tiny blue-green pinpricks of light, glowworms, each one glowing to lure its dinner, strung across the rock above you like a galaxy you could reach up and touch. Nobody speaks. There is just the drip of water, the dark, and that impossible living constellation overhead.

No photos are allowed, and for once I did not mind. A phone could not capture it anyway, and the no-cameras rule means everyone simply sits in the dark and looks, which is exactly right. We came out blinking and a little stunned, the way you do after something genuinely new.

It is a short experience and an easy one, no fitness required, and I would not skip it. We had never seen anything quite like it, and I suspect you have not either. Of all the easy, low-effort things we did on the South Island, this is the one that surprised us most.

Photos: glowworm cave images courtesy of RealNZ and Southland NZ (photography isn't permitted inside the caves).