They are the remnants of charcoal production, an industry that once occupied the wooded hillsides of this valley in Co. Wicklow with a quiet, smoky intensity that left almost no trace in the popular imagination of the place.

Charcoal was made by stacking cordwood into carefully managed heaps, covering them with earth or turf, and burning them slowly with restricted airflow over several days. The process required level ground, and where the terrain was uneven, workers cut and built up flat platforms to create a working surface, these are known as pitstead or hearth platforms. At Glendalough, around seventy-five such 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 valley's early medieval stone churches. The platforms are roughly oval in shape, measuring approximately nine metres by six metres, a scale consistent with the dimensions needed to construct a substantial charcoal burn. A further forty similar platforms were noted separately, and at least one possible hut site has been identified in association with the complex, suggesting that workers may have lived on site, at least temporarily, during production seasons. The platforms were first documented by Ua Riain in 1940 and recorded again by Healy in 1972.