They are the remnants of charcoal production, an industrial process that once left its mark across this famously monastic valley in County Wicklow. Each platform, roughly nine metres by six metres, was levelled into the hillside to create a stable working surface where timber could be stacked into a mound, covered with turf or earth, and burned slowly over several days to drive off moisture and volatile compounds, leaving dense charcoal behind. The technical term for these clearings is charcoal-burning hearths or pitsteads, and once you know what to look for, they are unmistakeable.

The extent of the site is considerable. Around seventy-five of these platforms have been recorded on the northern and southern sides of the Upper Lake and to the west and south-west of Reefert Church, one of the well-preserved Romanesque ruins for which Glendalough is known. A further forty similar platforms were identified in subsequent survey work. The platforms sit at irregular intervals rather than in any organised grid, suggesting they were laid out pragmatically, following the terrain and the availability of suitable timber. References to the site appear in scholarly work from as early as 1940, cited by Ua Riain, and were followed up by Healy in 1972, indicating that the features were recognised by researchers long before industrial heritage of this kind attracted much wider attention. Charcoal production in Ireland was closely tied to iron smelting and other metalworking industries, and Wicklow, with its combination of woodland, water, and mineral resources, was well placed to support such activity.