Loch Laggan is a long, freshwater loch lying amongst the mountains east of Fort William. It is high amongst the mountains, a ribbon of water at the top of Glen Spean, between Badenoch to the southwest, the Monadhliath Mountains to the north and Lochaber to the west. The A86 road from Spean Bridge to Kingussie follows along its north shore.
The loch is fed at its head by the River Pattack, entering at the hamlet Kinloch Laggan. This eastern end of the loch includes the largest freshwater beach in Britain.
The river emerging from its foot is the River Spean, which vanishes into Loch Moy, which has been created in its current form as a dammed reservoir.
Since 1934, Loch Laggan has provided a reservoir, known as Loch Moy, lying below the main loch. This loch is not entirely artificial, but its current form is created by the Laggan Dam at its foot. Loch Moy separated from Loch Laggan by just a mile of ground in the glen. It forms part of the Lochaber Hydro-Electric Scheme.
Engineering operations from 1884-5 at the southeast corner of Loch Moy revealed an obstruction in the form of an accumulation of large stones mixed with clay. It is thought to be possibly the remains of a dam built c. 1410-20 by the Clan Cummings, in an abortive attempt to drown the MacKintoshes who inhabited Castle Moy.
The River Spean emerges from the foot of Loch Moy below the dam as a broad river meandering its way towards the River Lochy.
Loch Laggan (mostly its castle) is featured in the Temeraire series of novels; it is used as a base to raise dragons, because of geothermal heat sources.
The loch featured in the popular BBC series Monarch of the Glen as 'Loch Bogle'.
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