It is, in fact, the remains of a burnt mound, a type of prehistoric site found widely across Ireland and Britain, typically associated with the heating of water through fire-cracked stones. The process left behind exactly what survives here: dense accumulations of small angular stones in a matrix of dark, charred soil.

The mound at Knockalegan is irregular in plan, measuring roughly 11.4 metres north to south and 9.6 metres east to west, with a slight height variation, rising from around 0.4 to 0.5 metres at the northern end to about 0.65 metres at the south. It no longer reads as a single coherent form. Recent disturbance, including tractor activity that cut an east to west depression roughly two metres wide across the middle, has split what remains into three close-set rises. The two southern rises, each around five metres in diameter, sit beside one another with a shallow dip between them; the third lies to the north, separated by that tractor track. A property wall running east to west intervenes between the mound and a natural rise a few metres to the northwest, complicating any straightforward reading of the original topography. What makes the site particularly interesting is its company. A second burnt mound lies roughly 100 metres to the east in the same field, and approximately 80 to 100 metres to the southeast there is both another burnt mound and a fulacht fia, the term often used interchangeably with burnt mound but more specifically associated with the trough or pit where heated stones were dropped into water. Finding one such site in a field is notable; finding a cluster of four in such close proximity suggests this low, boggy ground was returned to repeatedly, across what may have been a considerable span of prehistoric time.