Derry Cairngorm is a six/seven-kilometre-long ridge-type mountain that runs north to south, it rises from Glen Luibeg in the south and concludes at Coire Etchachan in the north, where it is joined to Beinn Mheadhoin. Coire Etchachan has Loch Etchachan lying within it, at a height of 930 metres the highest notable expanse of water in Great Britain. It has trout living in it. On its eastern flanks the mountain falls steeply and craggily into Glen Derry while its western flanks descend more moderately to the valley of the infant Luibeg Burn. Derry Cairngorm is characterised by large granite boulders on its higher slopes which make walking in the summit area difficult, the walker often having to resort to hopping between boulders. This large expanse of boulders is formed by the action of freezing and thawing in a periglacial environment and is known as a blockfield or felsenmeer. All drainage from the mountain flows south via the Derry and Luibeg burns to join the River Dee, eventually reaching the sea at Aberdeen.