Northern Sweden's Ancient Stronghold: Mjälleborgen

Mjälleborgen, at Öneberget on Frösön in Jämtland, Sweden, stands as one of the northernmost fornborgs, built during the Roman Iron Age in the 300s. It is strategically placed, allowing those who controlled it to oversee the area around Frösön and the roads leading to Trøndelag or Medelpad. As one of Norrland's largest construction projects from prehistory, Mjälleborgen is a clear evidence of a organized regional society, which thrived during the 400s to 500s, as stated by the source.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons