Orsa, Sweden Orsa, Sweden Orsa is a locality and the seat of Orsa Municipality, Dalarna County, Sweden, with 5,308 inhabitants (2010). It is located in the northern part of lake Siljan, about north of the town Mora. Inlandsbanan and European route E45 run through the town and the railroad Bollnäs-Orsa connects. The southern parts of Orsa are characterized by the Siljan Ring, the ring of lakes and rivers in northern Dalarna formed by the big meteorite strike 365 million years ago. In central Orsa, at the ouflow of river Oreälven a sand bank has been built up, in these days enjoyed by
Siljan Ring Ordovician and Silurian sedimentary rocks deformed by the impact are rich in fossils. The area around the Siljan Ring has been the site of recent prospecting for oil and natural gas, though none of the projects has so far been commercially viable. There are large deposits of lead and zinc near Boda at the eastern edge of the Ring. There are several lakes in the vicinity, the largest of which is Siljan on the south-southwestern edge of the crater, with the smaller Lake Orsa to the west and Skattungen and Ore on the northeastern margin. The Siljan Ring consists of