Fly Geyser aka Fly Ranch Geyser located in Nevada on a private land is somewhat not whole natural, because this was accidentally created during a drilling expedition in 1964 while exploring for sources of geothermal energy. The drilled well may not have been capped properly or left unplugged and dissolved minerals started rising and accumulating, creating the travertine mound on which the geyser sits and continues growing. Its currently about 1.5m high and 3.7m wide.
In June 2016, the non-profit Burning Man Project announced that they had purchased the Fly Ranch, including the geyser, for $6.5 million. The Burning Man Project is planning to provide controlled access to the property in the future.