Stars twinkle in the inky blackness, constellations never before seen, emitting beams of light tinged with green. A myriad galaxies swirl by, like so many Milky Way’s, with such dizzying regularity that I’m starting to wonder if I’m not on some intercosmic mission.

Constant cold drips of water on my head and the rush of a nearby waterfall rescue me from my reverie: this is the Te Ana o te Atua cave, otherwise known as the Cave of the Spirit, part of the larger Mangawhitikau Cave system in the Waitomo District and I’m floating on an underground river aboard a raft admiring constellations of the glow-worm kind.

The waterfall becomes progressively louder and as I start to wonder if this is a blackwater-rafting trip after all, Katy, our tour guide from Spellbound for the morning, flicks on the light on her safety helmet. She instructs us all to do likewise as we approach a dock that leads to a large cavern. Glancing around, it’s clear that most of the others are ready to disembark – it’s not that we’re scaredy-cats, but most of its punters have selected a Spellbound trip for a particular reason: a wetsuit-free cave adventure. It's an ideal way to explore if you're travelling with children, or in a group with differing adventure levels, or you simply don't fancy getting too wet!

We follow a narrow pathway into another large glow-worm paradise where Katy explains that these little creatures are not worms, but the larval form of a mosquito-like fly called Arachnocampa luminosa, which belongs to the global family of fungus gnats. The adult fly lives for two to five days and its sole function is to reproduce. To do so, the female adult glows to attract the male, and after fertilisation, lays around 130 eggs in rock crevices.

“When the larvae hatch they spin nests of silk and mucus, attach sticky fishing lines of ten to 15 centimetres in length, then start to glow,” says Katy. “The light attracts small flying insects trapped in the cave, and when they see the glow-worms, they think it’s an escape route, but instead they become glow-worm tucker.”

We take another leisurely float in our inflatable raft back through the galaxies of light to see a glow-worm fishing line – close up. Each glow-worm seems to have around 20 to 40 dewy and sticky-looking threads hanging from its nest. Then we hike through the caves beside the river, and emerge in a clearing in the native bush. Katy passes drinks and cookies around saying that farmers used to consider the caves a nuisance. “They planted trees to stop their livestock falling into them, but these days they’re wondering how many people they can squeeze through!”

Back in Waitomo village, I call into the Waitomo Caves Discovery Centre. It’s a great place to start exploration of the region. A giant replica of a fossilised ammonite found nearby in Taharoa in 1977 kicks off a series of incredible displays on Waitomo’s karst landscapes and the different rocks that can be found in the region, while a multimedia show, Arachnocampa Luminosa, tells the story of the NZ glow-worm. Other topics covered include cave dwellers, early exploration of the area, the different types of cave formations and the fossilised bones that can be found within them, including bat, moa and kiwi. Kids (of all ages!) were making the most of the opportunity to experience the feeling of being underground in the museum's cave crawl, a tight squeeze through a cunningly constructed ‘rock’ wall.