Is the place where it smells like rotten eggs (presence of hydrogen sulfide) and there are plenty of mud volcanoes and geysers. Mud so much that it forms a mud pools, and you can see in this photo. Thermal activity here is due to Rotorua caldera, which is a city of the same name. By the way, the water here is very different colors - from yellow to orange to green. So many tourists come to see this miracle.