Unmelting Snow is a quest item used in Repairing the Phial. It can be found at Throat of the World, just south of the destroyed Word Wall and up the slope of the mountain.
Legend[]
According to Quintus Navale, the patch of snow has never melted because the Greybeards taught it to ignore the sun, so the heat simply washed over it. The original White Phial was made from this snow.