Vänern ( , also , ) is the largest lake in Sweden, the largest lake in the European Union and the third-largest lake of all Europe after Ladoga and Onega in Russia. It is located in the provinces of Västergötland, Dalsland, and Värmland in the southwest of the country. With its surface located at with a maximum depth of , the lowest point of the Vänern basin is at below sea level. The average depth is at a more modest , which means that the average point of the lake floor remains above sea level. Vänern drains into Göta älv towards Gothenburg and the Kattegat tributary of the Atlantic Ocean. It is the only one of the ten largest lakes in Sweden not to drain on the country's eastern coastline. Due to the construction of Göta Canal in the 19th century, there is an upstream water path to Vättern and the east coast from Vänern. The main inflow of water comes from Klarälven entering Vänern near Karlstad with its source in Trøndelag in Norway. History The southeastern part of the Vänern is a depression that appears to have come into being by erosion of Paleozoic-aged sedimentary rock during the Quaternary glaciation that reached to the area. This erosion would have re-exposed parts of the Sub-Cambrian peneplain. Because the southern and eastern shores are parts where the Sub-Cambrian peneplain gently tilts towards the north and west, respectively, the lake is rather shallow at these places. The western shore of the lake largely follows a fault scarp associated to Vänern-Göta Fault. The modern lake was formed after the Quaternary glaciation about 10,000 years ago; when the ice melted, the entire width of Sweden was covered in water, creating a strait between Kattegat and the Gulf of Bothnia. Due to the fact that ensuing post-glacial rebound surpassed concurrent sea-level rise, lake Vänern became a part of the Ancylus Lake that occupied the Baltic basin. Vänern was connected to Ancylus Lake by a strait at Degerfors, Värmland. Further uplifting made lakes such as Vänern and Vättern become cut off from the Baltic. As a result, there are still species remaining from the ice age not normally encountered in freshwater lakes, such as the amphipod Monoporeia affinis. A Viking ship was found on the lake's bottom on May 6, 2009. A story told by the 13th-century Icelandic mythographer Snorri Sturluson in his Prose Edda about