If one walks along the old military road from Småbrekkane in Bergsdalen and in toward the mountains, one comes to Moastølen after about 2 km. The arcs lie like thick layers of loose sediments. The loose deposits come from Moagjelet, the vast river canyon just above the mountain farm. These deposits give good growing conditions for the forest - the birch forest is therefore much more lush at Moastølen than in the more barren mountains close by. Many of the trees are unusually large with trunk diameters of up to 70 cm. Several stumps are rotting, or are completely hollowed. Their age is unknown, but it is not impossible that some of the trees are over 200 years old. The birch has been able to grow freely, and some of the trees have died of old age in the end.
It is rare to see a full-grown birch, especially in the vicinity of a mountain farm. There was mountain farming at Moastølen until 1910, and the animals had grazed between the old birches. When the mountain farm ceased to operate or the grazing was reduced, the forest began to grow back. The new generation of birch therefore grows much denser than the roughly hundred "old timers" in the troll forest.