The.obvious spots are the geothermal sites such as Whakarewarewa. They are right on the edge of town. Even the park in the middle of town has steaming lakes and bubbling mud pools. The Redwood Forest in the direction of the airport is good walking, quite a few trails Apart from the main lake, the Blue Lake, Green Lake and Lake Tarawera are worth a trip.
If you want an Adrenalin ride, there are several street luge runs in the Skyline Gravity Park.