During the Bronze and Iron Ages, the Upper and Lower Rudasjöarna were connected and were part of a navigable watercourse that continued through Drevviken to Kalvfjärden and the Baltic Sea. Through the land uplift , the contact was lost, but remnants of such connection and settlement are preserved at Övre Rudasjön, where the ancient castle Ruda skans probably dates from the Bronze Age. Today there is only a small river left between the lakes.
