Lough Salt is a tarn lake located at the foot of Lough Salt Mountain. A Tarn lake is a small mountain lake, especially one set in a glaciated steep-walled amphitheatre known as a cirque. In common with most lakes in Ireland, this was formed due to the actions of glaciers in one of the Ice Ages (more than 40,000 years ago). Lough Salt takes it name from the Irish Lough 's Alt - Lough agus Alt (lake and Cliff) which refers to the steeps slopes of the mountain overlooking the lake.
The lake measures approximately 1.6Km long and 0.4Km at its widest. The exact depth is unknown. A survey of water resources in the early 1980's put the depth in excess of 60m (this was the maximum depth of the depth sounding equipment used). Tradition has it that the lake is as deep as the mountain is high (210m). Some old guide books give 72m as the depth. The lake supplies much of the water to the town of Letterkenny.
Until the road from Kilmacrennan through Termon was opened in the late 1830's, this was the main road from Letterkenny to Creeslough and Carrigart. An account of 1783 says "It is a very frightful pass of a quarter of a mile, the descent of the road being steep, the mountain rising over it to a vast height and often dropping down rocks from its abrupt precipices and the no less frightful lake below, sure to swallow up the traveller if he makes the least false step. And to make this place still more dismal, from the height of this declivity, the eye is shocked with an unbounded prospect, especially to the southwest, of barren mountains rising in endless groups beyond one another without one agreeable object or spot of green to relieve it". As Margaret Carton says in her fine book, 'what shocked the traveller's eye over 200 years ago a positive delight to many who live in today's cluttered world, a place of singular tranquility and solitude ..."
There is a very good walk around the lake and up to the top of Lough Salt Mountain. See Glen Walks for details.