After a quick refuel at Turangi's cute-as-a-button Thyme for Food Cafe - more 50s furnishings, Formica and chrome than you can shake a stick at - we were off to the Tongariro National Trout Centre.
The massive trout gazed up at us, keen to be fed. These enormous creatures clearly have their wishes regularly granted and they swam and schooled in search of treats.
At the Trout Centre you can learn everything you ever wanted to know about trout (and other freshwater creatures) and the exhibits of all things related to fly fishing are fabulous.
The aquariums are similarly riveting: koura, our native crayfish, full-grown whitebait whose lives weren't frittered away, as well as undulating long fin eels.
The highlight was being issued with a fishing licence and catching a rainbow trout - with a bit of assistance, my son caught a 1.1kg whopper. Pete, our friendly, informative DoC guide, smoked our catch using manuka bark peeled from a nearby tree and the result was delicious.
Keen for a little less wilderness and a bit more comfort, we were beckoned by the plush elegance of The Chateau. This chocolate box-building is a trip back in time; looking out the enormous picture windows to the mountains, it's fun to imagine being an intrepid explorer touring the colonies in style.
Sadly we couldn't completely do justice to the breakfast buffet because we were going caving. I'd have hated to find myself wedged between rocks on account of an extra hash brown. Feeling suitably svelte for spelunking, we drove with Brian, the DoC ranger, to Okupata Caves, 25 minutes from Whakapapa.
This unmarked network of underground passages is most impressive, but you do need to know what you're doing - or have Brian (who kitted us out with torches and helmets) and Jerome from Kiwis for Kiwi along for the ride.
We descended a sturdy ladder into a whole other world. Glowworms are native to New Zealand, which I didn't know. Also unique to New Zealand is the cave weta; colonies of them twitched their antennae, observing us as keenly as we watched them. Following Brian through ankle-deep water, we posted ourselves through a slot called the letterbox, a tight little challenge.
Next, kiwi. Jerome helped us locate nearby birds by scanning for their transmitters with a device that looked like a handheld television aerial to check for signals. No luck, disappointingly.
No longer city-tame, we were ready to return to town.
NEED TO KNOW
For further information see: Tongariro River Rafting, the Tongariro National Trout Centre and Chateau Tongariro Hotel.
Jerome and Brian are both part of Mahi Aroha, DoC's Summer Nature Programme, which includes hikes, fishing and cycling trips and an evening Kiwi in the Wild trip.
Elisabeth was a guest of Great Lake Taupo.