Several lakes recently formed at the bottom of the Upper Theodul Glacier, west of Trockener Steg. The largest, named Theodulgletschersee is 7.76 ha wide and lies at an elevation of 2,851 metres above sea level. It is the highest lake over 4 ha in Switzerland and the largest lake in the Matter Valley (the valley of Zermatt). The second-largest, named Furggsee is 2.57 ha wide and lies at 2,874 metres.