The canton of Glarus is dominated by the deep valley of the Linth River and the smaller Sernftal on the east. Most of the area is mountainous. The highest peak in the Glarus Alps is the Tödi at Other mountains include the Hausstock () and the Glärnisch (). The canton contains part of a thrust fault that was declared a geologic UNESCO world heritage site, under the name Swiss Tectonic Arena Sardona, in 2008. Famous outcrops in the Swiss Tectonic Arena Sardona include those at Lochsite near Glarus and in a mountain cliff called Tschingelhörner between Elm and Flims (in the same cliff is a natural hole called the Martinsloch). There is also a large lake called Walensee (Lake Walen) on the north. The total area of the canton of Glarus is , of which about half is considered productive. Forestry is an important branch of industry in the canton.