The Scottish Highlands are one of three regions in Scotland. The Highlands lie to the north and west of the Highland Boundary Fault and cover two thirds of Scotland. The Scottish Highlands are a rugged, mountainous area. The most rugged terrain is found on Scotland's western coast. The deepest valley, Glen Mor, divides the Highland's in two. The Northwest Highlands range sits on one side, the Grampian Mountains on the other. Much of the highlands are a broad treeless landscape known as a moor. A great deal of the moor is a soggy bog. The Highlands are a sparsely populated region. Most Highlanders, as residents of the Highlands are called, live on narrow coastal plains. The Highlands differ from the rest of Scotland in both language and culture. Historically, Highlanders spoke Gaelic and were staunch Roman Catholics.