Have you ever seen a cave full of glow worms? They make constellations of tiny green lights above you, like a kid's room with those glowing stars stuck to the ceiling, only cooler.
We started our day in Auckland, as possibly the first people ever to be picked up at the Westin by the bright green Jucy Budget Rentals van. Not that I was embarrassed, of course. I'm sure all those people were just impressed by our forethought and economy.
Speaking of economy, the car that the van delivered us to could probably have fit in the average SUV's wheel well, with a pickup that reminded me of some of those old Bug commercials. (Zero to Sixty. Eventually.) But that was not exactly a bad thing; the roads here are narrow and gas prices are high. But anyway, none of those were our main concerns when we took to the roads; we were focused entirely on looking right, keeping left and not dying, respectively. It was all rather stressful.
The Waitomo caves are not that far from Auckland, but they're not that close either. To get to them, one drives south for about two hours, through green and rolling hills, past large numbers of sheep and cows (and more sheep, and more cows) who look like they are never going to be able to eat all of that grass, but by God they're going to try. You can stop and eat a meat pie at a roadside cafe, but it isn't recommended.
Eventually, you will reach the turnoff for the caves and take it, as soon as you figure out which lane to turn in to. (It can be tricky.) This being a popular backpackers stop, you have to get past the various "adventure travel" offerings, (I have noticed that, as nice as these New Zealanders seem, their automatic response to tourists is to try and throw them off, out of, and down things. I wonder about that.) then you buy your ticket and follow your guide down into the caves.
I will admit, judging by the standard of Carlsbad, the Waitomo caves were not large, nor extensively decorated. But, unlike the dead landscape of New Mexico, these caves have an active river running through them, supporting a whole underground ecosystem; most notably, the glow worms.
I could tell you all about the glow worms, their dietary requirements and their life cycles, but I figure that's the sort of thing you could look up if you are interested (and you're not, I can tell). So I'll just boil it down to the essentials here: they're worms* and they glow. And when you're in a boat, moving silently along an underground river and there are bunches and bunches of them glowing over your head, it's pretty damn cool.