Each measures roughly nine metres by six, and to the untrained eye they read as nothing more than gentle terraces in the forest floor. In fact, they are the physical remnants of charcoal production, an industry that once operated quietly alongside the more celebrated monastic and mining history of the glen.

Charcoal-making platforms, sometimes called hearths or pitsteads, were created by levelling a section of sloped ground to provide a flat, stable surface on which a carefully stacked mound of wood could be slow-burned under a covering of turf or damp earth, a process that drove off moisture and volatile compounds to leave behind the dense, high-carbon fuel that smelting and smithing demanded. The platforms at Glendalough were recorded by Ua Riain in 1940, who noted around 75 examples on the northern and southern sides of the Upper Lake. A later study by Healy in 1972 identified a further 40 platforms of similar form and dimension. Together, the two accounts describe a surprisingly extensive operation distributed across the landscape rather than concentrated in a single spot, suggesting production at some scale over a sustained period, though the precise dating of activity at the site has not been firmly established in the available record.