Roughly nine metres long and six metres wide, these flattened earthen terraces were not foundations for buildings or field boundaries. They were the workplaces of charcoal burners, each one a hearth where slow-burning, smothered timber fires once produced the dense, carbon-rich fuel that ironworking and other industries demanded in quantity.

Charcoal-making platforms of this kind, sometimes called pitstead or hearth platforms, were created by levelling a section of hillside to provide a stable, roughly horizontal surface on which a carefully stacked pile of timber could be built, covered with turf and earth, and left to smoulder under controlled conditions for days at a time. The craft required constant attention and considerable skill to manage the airflow and prevent the wood from simply burning away. At Glendalough, the platforms cluster on the northern and southern sides of the Upper Lake and extend westward and south-westward of Reefert Church, one of the monastic complex's smaller Romanesque stone churches. Ua Riain recorded 75 such platforms in 1940, and a later survey by Healy in 1972 noted 40 comparable examples in the same vicinity. Whether these represent the same features counted differently, or partially overlapping surveys, is not entirely clear, but even the lower figure points to an industrial operation of considerable scale for the area.

The presence of so many platforms close to a major early medieval monastic site raises quiet questions about the relationship between the community at Glendalough and the industries that supported it. Charcoal production on this scale implies sustained demand, most likely connected to metalworking, whether for ecclesiastical objects, tools, or both. The platforms themselves survive as low earthworks, unobtrusive in the forest floor but legible once you begin to recognise their regular, levelled outline among the natural undulations of the hillside.