About 10 kilometres south of Vaasa, Söderfjärden is one of the largest confirmed meteorite impact craters in Finland — six kilometres in diameter, formed roughly 520 million years ago. You would not know it to drive through. The crater has been filled over geological time with sediment, turned by erosion into a basin of flat farmland and marshland, and is now one of the most productive agricultural areas in Ostrobothnia.
The crater rim, a low wooded ridge, is visible from the road if you know to look for it. The area is also an important nature reserve: the flat floor of the former crater acts as a staging ground for migrating cranes every autumn, and tens of thousands of cranes can gather here in September and October — one of the great wildlife spectacles of western Finland.