Like its cousins around Torridon to the south, An Teallach is built from Torridonian sandstone -- rock laid down as sediment roughly a billion years ago, long before complex life existed. The stone gives the mountain its characteristic stepped profile: horizontal bands of reddish-brown rock form natural terraces on the flanks, while erosion has carved vertical gullies between buttresses. The result, seen from Little Loch Broom to the south or from the road near Dundonnell, is a skyline that looks almost architectural, as though something immense was half-built and abandoned.

An Teallach's reputation rests on the Corrag Bhuidhe pinnacles, a series of sandstone towers that rise above the dark waters of Loch Toll an Lochain. The most dramatic feature is Lord Berkeley's Seat, an overhanging pinnacle at 1,030 metres where the ridge narrows to a few feet of exposed rock with vertical drops on either side. Scramblers can cross directly over the pinnacles -- a route graded as a serious undertaking -- or take a bypass path on the southwest side, though this eroded alternative is no casual stroll. The traverse from Sail Liath in the south to Bidean a' Ghlas Thuill in the north covers some of the most exhilarating ground in the Scottish Highlands.

Three main approaches lead to the tops. The most straightforward starts from Dundonnell, following a good path over rising ground for about six kilometres to reach Bidean a' Ghlas Thuill directly. A second route climbs steeply from Corrie Hallie, four kilometres south of Dundonnell, ascending the headwall of Glas Tholl to join the main ridge. Both paths deliver walkers to the summits efficiently but miss the central drama of the mountain. For that, the southern approach is essential: starting near Corrie Hallie, a track leads southwest for five kilometres before turning north to gain the ridge at Sail Liath, the gateway to the full Corrag Bhuidhe traverse.

An Teallach stands in Dundonnell Forest, west of the A832 road, in a landscape of lochs, moorland, and near-total solitude. To the south, Loch na Sealga fills a glacial valley; to the north, Little Loch Broom opens toward the sea. The mountain's relative isolation -- there are no other peaks of comparable height nearby -- gives it an outsized presence in the landscape. From the air or from the coast, An Teallach dominates the skyline of Wester Ross in a way that taller but more crowded mountains in the Cairngorms or Glen Coe cannot. It is not the highest mountain in Scotland, but many hillwalkers consider it the finest.