Beneath that subtle dip in the vegetation lies a burnt mound, a type of prehistoric site found widely across Ireland and Britain, typically consisting of a crescent or horseshoe-shaped heap of fire-cracked stone and charcoal-rich soil, thought to represent the accumulated waste from repeated episodes of water-heating, perhaps for cooking, bathing, or industrial processes. The mound at Greenwood, when examined in 1998, had been levelled to the point where it was barely a feature in the landscape, its roughly semi-circular spread of around twelve metres in diameter betrayed mainly by patches of blackened earth showing through where the vegetation had worn away entirely.

What makes this particular spot quietly remarkable is not the single mound in isolation but the clustering of similar features around it. Within a radius of two hundred metres, at least two other burnt mounds have been recorded, one approximately 130 metres to the west-north-west and another around 200 metres to the north-north-north-west, with a possible related burnt spread lying just twenty-five metres to the south-east of this one. The straight edge of the semi-circle faces south-west, oriented towards the lake, which is consistent with the general pattern seen at burnt mound sites elsewhere, where proximity to a water source was presumably essential to whatever activities were taking place. Whether this cluster around Bekan Lough represents repeated use of the same shoreline over generations, or a more concentrated period of activity shared across the immediate area, is not something the visible remains can answer on their own.