Gunnuhver is an area of mud pools and steam springs on the Reykjanes Peninsula. It is part of the UNESCO Global Geopark Reykjanes and is a protected area.
However, the area is named after the witch Gunna, who is said to have once lived here.
When Guðrun Önundardóttir, nicknamed Gunna, could no longer pay her landlord, Vilhjálmur Jónsson, her only possession, a cauldron. As a result, Gunna went mad and died.
As her coffin was carried to the cemetery, the pallbearers noticed it becoming lighter and lighter. As they dug the grave, they heard a voice whispering: "Don't dig deep, I won't stay there long."
The night after Gunna's funeral, her landlord was found badly injured and dead in a field with broken bones. His wife also died soon after. Gunna continued to haunt the area in the aftermath. She appeared to people, causing them to go mad or die.
They sought advice from Pastor Eiríkur of Vogsósar. The magic-savvy pastor was supposed to banish Gunna's haunting. He gave them a ball of wool. Gunna was to grasp the loose end, then they were to roll the ball to a place where Gunna could do no harm. The ball of wool rolled into a spring. Gunna followed the thread and plunged into the spring, which has since been called Gunnuhver.