These are the remnants of charcoal production, a process once central to iron-working and other industries that demanded intense, sustained heat. To make charcoal, workers would construct large mounds of timber on levelled ground, cover them with earth or turf to restrict airflow, and allow the wood to smoulder slowly for days. Each platform, roughly nine metres by six metres, is what remains of one of those carefully prepared burning sites, known as hearths or pitsteads.

More than seventy of these platforms have been recorded in the area, appearing at irregular intervals on the northern and southern sides of the Upper Lake and to the west and southwest of Reefert Church, the small early medieval ruin that stands nearby. The concentration is striking. Ua Riain noted the platforms as far back as 1940, counting around seventy-five examples, and a later study by Healy in 1972 identified approximately forty similar features in the same general area. The relationship between this industrial activity and the famous monastic settlement of Glendalough is not spelled out directly by the available evidence, but the proximity to Reefert Church, one of the older ecclesiastical sites within the valley, is at least suggestive of a long history of human activity in these woods.