Waimangu Volcanic Rift Valley is the hydrothermal system created on 10 June 1886 by the volcanic eruption of Mount Tarawera, on the North Island of New Zealand. It encompasses Lake Rotomahana, the former site of the Pink and White Terraces. It was the location of the Waimangu Geyser, which was active from 1901 to 1904. The valley contains Frying Pan Lake, which is the largest hot spring in the world. It also contains the steaming and usually pale blue Inferno Crater Lake, the largest geyser-like feature in the world although the geyser itself cannot be seen since it plays at the bottom of the lake.
The valley is home to a population of wallaby and Black Swan, which according to local guides were introduced to the region from Western Australia by George Edward Grey in the 19th century. Native birds include Wood Pigeon, Tuis, Fantail, Bellbird and Pukeko. Further introduced bird species are Mynah, Magpie, Shining Cuckoo, Finch and Sparrow.
Waimangu is protected as a Scenic Reserve. Many of its geothermal features are ranked as Category A – extremely important, of international significance. The developing local native forest is also very important as it is the only current New Zealand instance of a bio-system re-establishing in an area following complete devastation by a volcanic eruption.