It looks, at first glance, like a natural feature, an overgrown hump of stone and vegetation about twenty metres across and a metre high. But traces of kerbing along its northern edge suggest something more deliberate, and the 1908 Ordnance Survey six-inch map records it as a distinct rectangular island, hinting at a time when it was more legible in the landscape than it is today.

The mound is believed to be a crannog, the term for an artificial or partly artificial island dwelling used extensively in Ireland and Scotland from the Bronze Age through to the early modern period. Crannogs were typically constructed by driving timber piles into a lakebed and piling up layers of stone, brush, peat, and other material to create a stable platform, often ringed with a timber palisade and connected to shore by a narrow causeway. At Drumreaske, however, none of the usual structural evidence, no piling, no clear sign of artificial construction, is currently visible. What remains is the oval cairn itself, sitting in water-logged ground within what has since become flooded woodland. The causeway that reaches it from the north-east may be a later addition rather than an original feature. The lough it sits in is a subrectangular body of water, roughly two hundred metres north to south and widening towards the south, which gives the crannog a quietly enclosed setting.