Riksantikvarieämbetet

Hjälmarsund in the north-west part of Södermanland is a strait in the large lake Hjälmaren. A charter, probably issued in 1184, states that the lands of the Cistercian monastery Julita stretch to the portus called Ialmansund. The term portus (port or harbour) in early Swedish documents always pertains to towns, not the numerous natural harbours. At Hjälmarsund a long range north-south land route along an esker met an east-west water route on Hjälmaren, with the esker continuing north to lake Mälaren and the sea. The site had the conditions to become a town. It probably was superseded by the town of Arboga on Mälaren, which was founded in the 13th century and was a harbour for iron export. Archaeologically, Hjälmarsund is virgin soil.