What looks, at a glance, like a slight natural rise in the ground is in fact a burnt mound, a type of prehistoric site found widely across Ireland and Britain. These monuments are the accumulated debris of repeated heating: stones were placed in fire, then plunged into water to heat it, most likely for cooking, bathing, or industrial processes. Over time the thermally cracked, fire-blackened stones were discarded in growing heaps, producing the characteristic dark, charcoal-rich soil that makes such sites recognisable even in section.

This particular mound measures roughly ten metres in diameter. Sitting on top of it are two separate heaps of shattered stone and black soil, each between two and three and a half metres across and about half a metre high, positioned roughly two metres apart. The most likely explanation for this divided appearance is disturbance caused when the conifers were planted directly on top of the mound. A field drain has cut into its north-western edge, and in that exposed section face the heat-shattered stone and charcoal-rich soil are clearly visible, offering an inadvertent cross-section through the archaeology. A tumbled field wall lies across the south-eastern edge, adding another layer of later interference. The mound's location beside a spring is no accident; proximity to a reliable water source was a practical requirement for however the site was being used. Notably, a second burnt mound lies just eight metres to the south-west, suggesting this corner of Grallagh saw sustained or repeated activity over time.