Norway’s northern regions lie within the Arctic Circle, where there are borders with Finland and Russia, while much of the long border with Sweden runs through the Scandinavian mountains. This range, sloping to the south-east, is 1,530 km in length and has its highest areas in the south of Norway, where Galdhopiggen, Norway’s highest point, reaches a peak of 2,469 m (8,100 ft). Almost all of Norway is high ground; in the north the country becomes narrower, with mountains overlooking the fjords and the islands along the coast, and in the center and south the mountains form a high plateau, where there are permanent ice fields. The only area of low ground is around the Oslo fjord and along the coast to Stavanger. The principal rivers are the Glomma, the Lagen, and Tanaelv. Some 6% of Norway’s area is inland water–mostly long, thin lakes. Two-thirds of the country is tundra, rock, or snowfields, and one-quarter is forested, so good agricultural land is rare. Less than 3% of Norway is cultivated, and these areas are in the south-east and in the river valleys. The mountains of Norway are rich in minerals; there are deposits of iron ore, copper, titanium, coal, zinc, lead, nickel, and pyrites, and large offshore reserves of petroleum and natural gas.