Waitomo glowworm caves
When it rains... go visit a cave. Drove down to the most famous ones in NZ, Waitomo Caves. They have been a tourist attraction since soon after their discovery in the 1880s. Of course in those days there were no steps, handrails or electrical lighting, just a set of placed ropes and a handful of candles. Pretty hard absailing, especially for the women in their uncomfortable Victorian dresses.
To make a cave their home glowworms require a river to run through it, but in 2004 the river rose so high it reached the ceiling and killed off the entire population. So new glowworms were drafted in and their numbers are nearly back to normal. They surround themselves in silky strings like a spider web and glow to attract insects, which they kill with poison they have on their skin. The two times I've seen them I hadn't noticed the strings, but this time we got a great view of them, most impressive.
After a bit of history and geology of the cave and a short explanation of the glowworm's lifecycle we all got on a boat and headed into the darkness. The sight of thousands of glowworms above you with their eerie blue-green light is spellbinding. We were all mesmerised for a few minutes looking at the constellations of bioluminescence as the boat slowly followed the river out to the daylight. A real shame you can't take photos - cynically I'd say to protect their intellectual copyright, though mostly I guess it's because you can't expect everybody to know how (or remember) to turn the flash off their camera. The light would disturb the glowworms.