This is Espevær

On October 7, 1975, mushroom hunters on the small car-free island of Espevær discovered an oval circle 26 meters long and 14 meters wide with a total circumference of 63 meters. The trace was depressed five to ten centimeters into the ground, as if something heavy had been standing there. The hypothetical object was estimated to have weighted somewhere between 50 and 60 metric tons. Cue UFO talk.

On April 22, 1976, the Norwegian Armed Forces visited the island to examine the ring. The delagation concluded that they had no reasonable conclusion.