They are not foundations, not graves, not the remnants of any building. Each one, roughly nine metres long and six metres wide, is a hearth platform, the kind of levelled, carefully prepared surface on which charcoal burners once stacked and slowly smouldered timber under a covering of earth and turf. Charcoal-making of this kind was a slow, labour-intensive process requiring constant attention over several days, and the platforms, known sometimes as pitstead or hearth sites, represent what was once a substantial industrial presence in a valley more often associated with early Christian monasticism.

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 ruins within the Glendalough complex. References in the work of Ua Riain, writing in 1940, recorded 75 of these oval features. Later work by Healy in 1972 noted a further 40 comparable platforms in the same general area. Whether these counts overlap or represent distinct surveys is not entirely clear, but either way the numbers suggest that charcoal production here was no minor or occasional activity. The proximity to the monastic site raises questions about the relationship between the two, though the platforms themselves offer no dates. Charcoal was a vital fuel for metalworking, and early Irish monasteries were often centres of skilled craft production, including the working of iron and bronze.