Churfirsten is a mountain range in the Canton of St. Gallen , Switzerland . They form the natural boundary between the canton's Toggenburg and Sarganserland districts. They are the southernmost range of the Appenzell Alps , separated from the Glarus Alps by the Seez river and Walensee . They consist of a limestone ridge running east to west, with the individual peaks formed by erosion. The ridge is defined much more sharply to the south than to the north, with an almost vertical drop of several hundred meters towards Walenstadtberg and eventually Lake Walensee at 419 m.