The Reporoa Caldera is a 10 km by 15 km caldera in New Zealand's Taupo Volcanic Zone. It formed some 230,000 years ago, in a large eruption that deposited approximately 100 km3 of tephra, forming the Kaingaroa Ignimbrite layer. It contains three rhyolitic lava domes (Deer Hill, Kairuru and Pukekahu) and is associated with three geothermal fields. These are the active Reporoa geothermal field in the caldera, The Waiotapu geothermal area north of the caldera rim, and the Broadlands thermal area to the south. The Waikato River runs through the southern half of the caldera.