The terrain of Scotland is predominantly mountainous but may be divided into three distinct regions, from north to south: the Highlands, the Central Lowlands, and the Southern Uplands. More than one-half of the land in Scotland is occupied by the Highlands, the most rugged region on the island of Great Britain and the least densely inhabited part of Scotland. The Highlands contain two parallel mountain chains that run roughly northeast to southwest. The rocky summits of the Highlands were carved by ancient glaciers and centuries of rain. Broken by deep ravines and valleys, the region is noted for its scenic grandeur. Precipitous cliffs, moorland plateaus, mountain lakes, sea lochs, swift-flowing streams, and dense thickets are common to the Highlands.

Dividing the parallel mountain ranges of the Highlands is a depression, or fault line, known as the Glen More, or the Great Glen. This depression extends southwest from Moray Firth on the eastern coast to Loch Linnhe on the western coast. Within the Great Glen is a chain of narrow lakes, or lochs, including Loch Ness. These natural lochs are linked by a series of artificial channels and together form the Caledonian Canal. Small craft can use this canal to sail through the Great Glen from coast to coast. To the northwest of the Great Glen lie heavily eroded peaks with fairly uniform elevations ranging from about 600 to 900 m (about 2,000 to 3,000 ft). Between the peaks are numerous valleys, known as glens, carved by glaciers. In the Highlands southeast of the Great Glen the topography is varied and spectacular. This region is traversed by the Grampian Mountains, the principal mountain system of Scotland. The highest peak of the Grampians is Ben Nevis (1,343 m/4,406 ft), the highest summit in the United Kingdom.

To the south of the Highlands lie the Central Lowlands, a low-lying belt of fertile valleys with an average elevation of 150 m (500 ft). Rich soils and most of the country’s coal deposits are found in the Lowlands. This region, which comprises just one-tenth of Scotland’s surface area, is home to Scotland’s leading industries and cities and the majority of the country’s population. Several chains of hills cross the Lowlands, including the Ochil and Sidlaw hills, as do several important rivers, notably the Clyde, Forth, and Tay.

The terrain of the Southern Uplands, a region less elevated and rugged than the Highlands, consists largely of a moorland plateau traversed by rolling valleys and broken by mountainous outcroppings. Only a few summits in the Southern Uplands exceed 760 m (2,500 ft) in elevation, the highest being Merrick (843 m/2,765 ft) in the southwest. The Cheviot Hills adjoin the Southern Uplands region along the boundary with England.