Each one measures roughly nine metres by six, just large enough to have once held a carefully constructed mound of timber, earth, and turf. These are the remains of a charcoal-making site, one of the largest concentrations of such platforms recorded in Ireland, and they speak to an industrial past that sits at some remove from the monastic story Glendalough is usually asked to tell.

Charcoal production relied on these levelled platforms, sometimes called hearths or pitsteads, where slow-burning timber stacks were smothered under earth and bracken and left to carbonise over several days. The resulting charcoal was far more efficient than raw wood as a fuel, essential for smelting iron and other metalworking processes. At Lugduff, seventy-five platforms have been identified on the northern and southern sides of the Upper Lake, with a further forty recorded to the west and south-west of Reefert Church, the small Romanesque ruin that stands nearby. The sites were noted by Ua Riain in 1940 and documented again by Healy in 1972, suggesting a spread significant enough to have drawn repeated attention. The sheer number of platforms implies sustained, organised production rather than occasional or opportunistic burning, though the precise period of activity is not recorded.