In the municipality of Korpo, on the village island of Jurmo, are some of the most studied antiquities in Southwestern Archipelago: so called monk rings. Interpreting these four stone circles has been tried already in the 18th century, when it was suspected that they were made by monks from the village of Kökar. It has been found that Franciscans really lived on Kökar Island from the end of the 14th century to the 1530s. So it might well be the case that the monks built these stone rings on their fishing trips, for example. Why did they do so, is still not known. One interpretation is that they are remnants of a kind om "tomtning".