The Tongariro National Park has Dual World Heritage status and contains 3 active volcanoes. You'll have the opportunity to throw the One Ring into the fires of Mount Doom. There's also a robust hut system, which means that you'll have a protected and warm spot to sleep if you go that route. Limited camping is also available, and the track can be hiked clockwise or counterclockwise.
Most people visiting Togariro National park do the 1 day Alpine Crossing. I opted to do the full circuit, a 27 mile hike that takes you all the way around the prominent summit of Mt. Ngaroe.
I traveled the trail clockwise, leaving from Whakapapa Village and heading to Waihohonu Hut on the first day. This part of the trail is fairly flat and winds 14.3 km around the south side of Ngaroe.
Day 2 brought a short 8km hike to the Oturere Hut. Since that didn't take very long, I day hiked up to the Emerald lakes and the Ketetahi hut. The sunset over Mt. Ngauruhoe and Mt. Tongariro from Oturere was spectacular.
On Day 3, I rose with the sun and tackled the trail up to Tongariro crossing and the Red Crater. I dropped my pack at the bottom of Ngauruhoe and summited early, before the tallus slopes were overrun with day hikers. Instead of stopping at the Mangatepopo Hut, I decided to finish off the loop, adding significant mileage, but all mostly downhill back to Whakapapa village.