About 2.5 hours south of Auckland, you'll encounter a truly unique city by the name of Rotorua. What makes Rotorua so special is its combination of exceptional geothermal activity (a big thanks to the Rotorua volcanic caldera for this), plentiful lakes, Maori culture, and a deluge of adventure activities. No wonder this has been a hot spot (geothermal activity? “Hot spot?” Get it? Get it???) for both international and domestic travelers for a long time.
When in Rotorua, you'll have no trouble a) finding hot springs and Maori culture, often in the same place and b) smelling rotten eggs. Both you'll get used to in no time. There are a lot of touristy stops in Rotorua, which is the downfall of having been so popular or so long; things tend to get a theme-park feel and tend to cost you some money. The Living Maori Village of Whakarewarewa is an excellent combination of Maori customs in a genuine, lived-in village and a number of geothermal pools and springs. The most basic tickets for entry will run you $35 NZD per adult. Te Puia, which encompasses the Pikirangi Village and the Geothermal Valley, is another instance of both Maori culture and a a grandiose geothermal area that includes the Pohutu Geyser, which goes off every few minutes and is known to spray water up to 30 meters (about 100 feet) into the air. The most basic Teu Puia experience is $48.50 NZD per adult. Other popular geothermal areas include the extensive, awe-inspiring Waimangu Volcanic Valley, which will run you $34.50 for about two hours of hiking and viewing, while Wai-O-Tapu provides a colorful selection of mud pools, volcanic craters, and much more for $32.50 NZD. Finally, the geothermal walk ($35 NZD) at Tikitere (Hell's Gate) is a bit further up Highway 30, but may be the most incredible look at boiling mud and steaming, volcanic vents you'll get in Rotorua. There are more, but we think you get the drift that this place is geothermal-crazy.
You'd be right to ask if there's anything else to do than stare at steaming pool; you'd also be happy to know that there is. The Whakarewarewa Forest just outside of town is a great location for hiking and mountain biking in the bush, with a ton of quality of trails that run through actual Redwoods. Nearby Mount Ngongotaha is where you can catch a gondola up for a fantastic view of the city and lake it's named after and is also popular for the luge ride back down. Plenty of hikes can be had from the quite-short to the day-long variety and are outlined in detail here.
We'd be remiss if we didn't mention the whitewater rafting before closing out the summary. The Kaituna River is an adventurer's dream, and is home to “the largest commercially rafted waterfall” in the world, while up to class IV and V rapids can be attempted within an hour away on the Wairoa, Rangitaiki, Mohaka, and Mokau Rivers. If this is your style, you'll need to try at least one of these trips during your New Zealand adventure.
Note:For Lord of the Rings lovers out there, the hobbit homes of Hobbiton still remain carved into the hills on a farm about an hour to the northwest in the town of Matamata.