These are; Kinnekulle, Halleberg, Hunneberg and Billingen. Along the Kattegat lies the archipelago usually known as the Gothenburg archipelago. The southern part of it, belonging to Gothenburg Municipality, is part of Västergötland. The northwestern border is demarcated by Sweden's largest lake Vänern, and the north-eastern border is demarcated by Sweden's second largest lake Vättern. Within the province the shoreline of Lake Vänern is long, and along Vättern it is . The largest river is Göta älv which drains Vänern to the east shore and the Kattegat strait; along the river several important cities and towns have been situated for centuries. The average rainfall is near the coast and in the plains. The average temperature is in January and in July. As of 31 December 2016, Västergötland had a population of 1,328,128 distributed over four counties:  There are many ancient remains in Västergötland. Among the most notable of these remains are the dolmens from the Funnelbeaker culture, in the Falköping area south of lake Vänern. Finnestorp, near Larv, was a weapons sacrificial site from the Iron Age. The population of Västergötland, the Viking "Geats" appear in the writings of the Greek Ptolemaios (as "Goutai"), and they appear as "Gautigoths" in Jordanes' work in the 6th century. The province of Västergötland represents the heartland of Götaland, once an independent petty kingdom with a long line of Geatish kings. These are mainly described in foreign sources (Frankish) and through legends. It is possible that Västergötland had the same king as the rest of Sweden at the time of the monk Ansgar's mission to Sweden in the 9th century, but both the date and nature of its inclusion into the Swedish kingdom is a matter of much debate. Some date it as early as the 6th century, based on the Swedish-Geatish wars in "Beowulf" epos; others date it as late as the 12th century. Västergötland received much early influence from the British Isles and is generally considered to be the bridgehead of Christianity's advance into Sweden.