The Monadh Liath is a kind of geological accident. When successive ice sheets covered Scotland during the Pleistocene, the great Cairngorms next door were carved into U-shaped valleys, gouged corries, and steep-walled glens. The Monadh Liath sat under the same ice, but the ice barely moved. It froze to the ground across the high plateau, locked in place rather than flowing, and so the landscape it left behind is a smoothed, rounded surface rather than a carved one. There are no real ridges, no proper corries away from the Munros fringe, only a few short glaciated troughs like Glen Killin on the north. Geologists have only recently understood the mechanism: ice on the plateau froze static, but as it began to flow down into the troughs at the edges, it thickened, accelerated, and warmed enough to erode them. The last enlargements happened during the Younger Dryas, around 12,000 years ago — recent, in geological terms, almost yesterday.

The main valley inside the Monadh Liath is the River Findhorn, and it is one of the most peculiar rivers in Scotland. Most Highland rivers run more or less straight, having been straightened by ice. The Findhorn winds. It is an incised meandering river valley — a relict of pre-glacial drainage that the ice never quite straightened out — turning back on itself in long looping bends as it cuts down through the plateau. The four Munros sit on the Spey rim: A'Chailleach at 930 metres, Geal Chàrn at 926, Càrn Sgulain at 920, and Càrn Dearg at 945. Three of them make a classic circuit walk from Newtonmore in a single very long day, and walkers tend to do them in that combination. The interior, where the Findhorn meanders, is rarely visited even by Munro-baggers. Two hours from the road, you can stand on heather moorland that has changed less over the last ten thousand years than almost anywhere else in Britain.

The remoteness is recent history, however, and it is being chipped away. The Beauly-Denny power transmission line was completed across Corrieyairack Pass, bringing high-capacity grid infrastructure into a region that had never carried it. The Glendoe Hydro Scheme above Fort Augustus came next: the reservoir and dam are modest, but the access roads needed to service all the weirs diverting water into the catchment have run heavy-duty tracks deep into ground that had no roads before. And the wind farms followed, built where the grid connection and the access roads now made them viable. From the Cairngorm summits, or from peaks in the Western Highlands as far as 50 miles away, the wind turbines now dominate the northwest skyline. The Monadh Liath is designated a Special Area of Conservation; it is also, simultaneously, an industrial landscape. Native woodland is mostly gone, eaten away over a thousand years by sheep, deer, and people. What remains is open, exposed, immense, and changing — but still, on the right grey day, still very much itself.