Each one measures roughly nine metres by six, just large enough to have once held a carefully stacked mound of timber, covered with earth and smouldering slowly over days to produce charcoal. These are the physical traces of a charcoal-making industry, and in their sheer number they suggest an operation of considerable scale.

Charcoal burning was a labour-intensive process that required flat, level ground on otherwise sloping terrain, which is why the platforms were cut and built up by hand, creating the oval earthen shelves that survive today. Around seventy-five of them have been recorded on the northern and southern sides of the Upper Lake, with a further cluster to the west and south-west of Reefert Church, one of the small Romanesque churches within the Glendalough complex. A separate group of around forty similar platforms has also been noted in the area. The platforms appear at irregular intervals rather than in any neat arrangement, suggesting that suitable ground, proximity to timber, and access routes all shaped where each one was positioned. The references to this site in the historical record date to observations made by Ua Riain in 1940 and Healy in 1972, though the platforms themselves are likely considerably older, connected to the demand for charcoal as fuel for iron-working or other industries in the wider region.

The platforms sit in landscape most people associate entirely with early medieval Christianity, which makes their industrial character quietly arresting. Reefert Church, near which several of the platforms cluster, is itself a modest ruin whose name is often translated as the burial place of kings, and the juxtaposition of monastic remains and industrial earthworks in the same woodland is a reminder that Glendalough was never only a place of prayer.