Trollsjön is Sweden's cleanest clear-water lake located 815 m above sea level in the end of the valley Kärkevagge at the foot of Gearggecorru and Vassejietnja. Trollsjön is a sterile mountain lake with meltwater from nearby glaciers. The visibility depth is 36 meter all the way to the bottom of the deepest part of the lake. The depth of sight would most likely been longer if the lake had been deeper. It’s estimated to be about 70 meters. Trollsjön means Trolls lake in Swedish and the name Rissajaure is the Sami name for Trollsjön and it roughly means the lake that glimmers like fire. The Kärkevagge valley is about 5.5 km long and is a labyrinthine landscape of large boulders. Kärkevagge means rocky valley, and hidden among these boulders are an estimated number of over 3000 caves in the walley floor.