[Oonoch Doo] Gaelic, meaning Dark Ridge.
Aonach Dubh is the ridge running north-east from the north end of Stob Coire nan Lochan, forming the westernmost of the Three Sisters. Its north face, dominated by the conspicuous slot of Ossian's Cave, looms over the glen.
The East, North and West faces of Aonach Dubh have very distinct characters. The east face has lots of separate steep crags, many of which have excellent rock climbing but limited winter climbing. Only the Far Eastern Buttress is included here, although a few ice-lines occasionally form elsewhere. The North Face is dark, vegetated and foreboding – a natural winter venue, but rarely in condition. The West Face has a sunnier, friendlier ambience and more continuous steep ground cleaved by deep gullies, providing excellent winter sport.