They are easy to overlook, easy to mistake for natural terracing or old cultivation ridges. In fact they are the remnants of an industry that once filled these quiet valleys with smoke: the making of charcoal.

Charcoal production relied on carefully managed, slow-burning mounds of timber. Workers would stack wood over a central flue, cover the whole pile with turf or earth to restrict airflow, and tend the burn over several days. The flattened, levelled platforms left behind, known as hearths or pitsteads, were essential preparation for this process, giving the mound a stable base on which to sit. At Glendalough, around 75 such platforms have been recorded, each roughly nine metres by six metres, arranged at irregular intervals across the landscape. A further 40 similar platforms were identified separately, bringing the total concentration to a remarkable scale. The sites were noted by Ua Riain in 1940 and subsequently by Healy in 1972, though neither source establishes a precise date for when the charcoal-making took place. The proximity to Reefert Church, one of the early ecclesiastical remains within the Glendalough complex, raises quiet questions about the relationship between monastic settlement and industrial activity in the valley, though no firm connection has been drawn.

The platforms are best appreciated by those already walking the woodland paths around the Upper Lake. They appear as shallow, level shelves in the sloped ground, their oval outlines softened by centuries of leaf litter and moss. Knowing what to look for makes all the difference; without that, they simply read as slight irregularities in the forest floor.