The Highland Boundary Fault runs across the region from the northeast to the southwest. This roughly divides the area between highland Perthshire, including part of the Grampian Mountains, to the north, and lowland Perthshire and Kinross to the south. The highland area is intersected with glacial valleys, often containing ribbon lakes, including Loch Tay and Loch Earn. The lowland area is a fertile region lying within the Central Lowlands.