From Halopedia, the Halo wiki
The Vigrond Highlands was an area near the city of Utgard on Harvest. It was the starting point of the Mimir River which cut just south of Utgard.
Upon the attack of Harvest by the Covenant ship Rapid Conversion, refugees from the small settlements in Vigrond Highlands fled to Utgard, the capital of Harvest.
Like most of the place names on Harvest, the Vigrond Highlands are named in reference to Norse mythology, where Vigrond is a giant plain where Ragnarök, the battle between the gods, will be fought.