What is "tryvann"

Tryvann is a small lake in Nordmarka, the forest area just north of Oslo city, near the Holmenkollen ski jump. By the water lies a cabin called Tryvannstua, in which there is a café open regularly during both summer and winter. On a hill above the lake looms the television tower Tryvannstårnet ("The Tryvann tower"), visible from most of Oslo. Tryvann is the entry and beginning of Nordmarka. It is used all year around. The key purposes of this area in the winter are skiing and cross-country skiing, whereas in the summer it is more commonly used for walks in the forest and biking. When referring to Tryvann, it is mostly referred to as the Tryvann vinterpark.