Frying Pan Lake
This is looking across the lake (it's around 50-60 °C), from the outflow. It's a part of Waimungu Volcanic Valley, which is my personal favourite of all of the thermal areas around Rotorua. From here the walk mostly follows the stream down to Lake Rotomahana, which was formed as a crater in the Mt Tarawera eruption in 1886 and which slowly filled with water until the 1930's and is now the deepest lake in the North Island of New Zealand.
Nearby to here is the site of a now extinct geyser which went off regularly every four days from 1904 to 1908, sending boulders the size of houses to heights of over 300 metres - really more of a regular eruption than what is typically thought of as a geyser.
I don't know if it still operates, but one of the best possible tours of the Rotorua area was to catch a bus to Waimungu, walk down to the lake for a tour around Rotomahana stopping half way to walk across to Hot Water Beach on Lake Tarawera for lunch. After lunch you then get picked up by the tour boat on Tarawera, tour around that lake and back to Tarawera Landing and then return to Rotorua via The Buried Village, and the Blue and Green Lakes. Quite a day out!
geothermal Waimungu Rotorua Rotomahana lake thermal Tarawera