What gives it away is the central depression opening towards the west, and the dark, stone-laden soil exposed where erosion has cut into its side. This is a fulacht fia, a type of monument found in considerable numbers across Ireland, typically interpreted as a Bronze Age cooking site. The usual understanding is that stones were heated in a fire, dropped into a water-filled trough to bring it to a boil, and the shattered, heat-cracked fragments were then discarded into a crescentic mound around the trough. That characteristic crescent or horseshoe shape, and the blackened, fire-fractured stone, are precisely what the Knockalegan mound displays.

The mound measures roughly 11.5 metres north to south and 13 metres east to west, though its precise limits are difficult to trace in places, particularly where it has been partially levelled. It sits at the boundary between average grazing land and a stretch of flat, reclaimed pasture that gives way to rush-grown boggy ground to the west and north-west. What makes the Knockalegan site quietly remarkable is not the mound itself in isolation but its company. Another burnt mound lies approximately 15 metres to the north, and two further examples are positioned around 95 to 100 metres away to the north-west and north-north-east. Finding four such monuments within a relatively compact area suggests this was not an incidental or one-off activity, but a landscape that saw repeated, possibly sustained use during prehistory, whether for cooking, processing hides, or other communal purposes that archaeologists still debate.