One area in Norway where I have hiked many times is in the mountains north of Valldal.
Trails here lead above the tree line through alpine tundra and mountain valleys, to the beautiful, cold waters of mountain lakes like Heimstevatnet, Fremstevatnet, Storvatnet, Brekkevatnet, and Kyrfonndalsvatnet. From Storvatnet trails lead onward, to areas beyond including the DNT cabin at Fokhaugstova.
On a recent autumn visit to Norway I hiked to Brekkevatnet and Kyrfonndalsvatnet, on a day trip with two of my cousins. The treeless landscapes provide sweeping, fantastic views. Walking these trails has a quiet, peaceful appeal hard to describe.