They measure roughly nine metres by six, just large enough to have once held a carefully stacked mound of timber covered with earth and moss, slowly smothering rather than burning. These are the remnants of charcoal production, an industrial process that sustained metalworking and other crafts long before coal became widely available. The platforms, sometimes called hearths or pitsteads, were where chargers, the workers who managed the slow burn, would tend their mounds for days at a time.

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 early medieval stone churches that form part of the wider Glendalough monastic complex. A further forty similar platforms were noted in the same general area. The first reference appears in work published by Ua Riain in 1940, with a later account by Healy in 1972 confirming the scale of the site. The concentration around Reefert is particularly striking; the church itself dates to the early Christian period, and the presence of industrial charcoal-making in such close proximity raises questions about the relationship between the monastery and the surrounding woodland economy, though the precise dates of the platforms are not firmly established.

The platforms are subtle features, and without knowing what to look for they read simply as uneven ground. Visitors exploring the quieter western reaches of the valley, away from the more heavily trafficked round tower and cathedral ruins, are most likely to come across them. The area around Reefert Church is accessible on foot from the main visitor centre via the Green Road along the southern lakeshore.