Visiting New Zealand, you're going to spend a lot of time outdoors, but how you spend it is up to you. The Redwood Treewalk was an experience I won't soon forget. I felt like one of the Lost Boys in Hook, that live in the trees, making my way through the forest across the numerous suspension bridges. It was so much fun!
Go figure, the first time I see a majestic California Redwood tree, it's in New Zealand. This was the second activity I chose in Rotorua on my Cheeky Kiwi Tour, I'm not affiliated with them. If you're driving on you're own, I think it would be amazing to do this at night. They offer a Nightlights tour. You can see the many unique lanterns they have set up around the forest and can just imagine how cool it would be.
There are 28 suspension bridges and 27 viewing platforms. If you're not into heights, you can stay on the ground and hike around the Whakarewarewa Forest, for free! There are several different trails to choose from. In addition to the Redwoods, there are so many fern trees. The Silver Fern is the national symbol of New Zealand. You can tell if it's a Silver Fern by looking at the underside of the leaf. It's not just a clever name, it's silver.
If you are into heights and adventure, they offer another option that's higher than the Treewalk: Redwoods Altitude. Here you'll walk on rope jungle bridges, zipline, and a final jump.