It is 358 m (1,175 ft) above sea level and has a volume of 8.816 km3 (2.115 cu mi).

[3] The 6.1-square-kilometre (2.4 sq mi) island Tjåehkere (Southern Sami) or Gudfjelløya (Norwegian) lies in the lake Tunnsjøen.

This makes Gudfjelløya the highest island within a lake in Norway (and in Europe).

It towers higher than the island of Monte Isola within Lake Iseo, in northern Italy.

Its highest point is 177 m (581 ft) above the lake's water surface.