Gunnuhver, Suðurnes, Island
is a high temperature area with temperatures over 300°C, with hissing and fuming solfatara and the biggest mud pool in Iceland. The caldera has a diameter of roughly twenty metres. If the wind is blowing in the right direction, a blue lake appears between the steam and the vapours. The ground water of the geothermal area is entirely made up of seawater.
According to myth the mud pool is named after the malignant witch Guðrún Önundardóttir, or shortly Gunna, who was supposed to have killed a couple. She was thrown into the sizzling spring and allegedly even now her ghost walks along the rim of the mud pool.