geographic region in the Grampian Mountains of Scotland, composed mainly of moorland and lochs (lakes). The region includes Loch Rannoch, part of the Tummel-Ericht hydroelectric scheme, and, south of the loch, Rannoch Moor, a bleak windswept area of 20 square miles (52 square km) of heather and peat bog with a few surviving pines, relics of the original Caledonian Forest of Scotland. The northeast section of the moor is a nature reserve.