The mound measures fourteen metres north to south and twelve metres east to west, rising only about thirty centimetres above the surrounding ground. That modest elevation is part of what makes these sites so easy to overlook, and so easy to plough through without recognising what they are.

A fulacht fia, sometimes spelled fulacht fiadh, is a type of prehistoric cooking site found in enormous numbers across Ireland, particularly in Bronze Age contexts. The characteristic mound forms from the accumulated debris of a repeated process: stones are heated in a fire, then dropped into a water-filled trough to bring it to the boil, and the thermally shattered fragments are raked aside after each use. Over generations, those discarded burnt stones accumulate into the horseshoe or oval mounds that survive today. The site at Coolvallanane Beg follows the pattern closely. A stream runs to the west of the mound, providing the reliable water source that these sites almost invariably require. And it does not stand alone: a second fulacht fia lies roughly fifty metres to the east, a pairing that suggests this particular stretch of ridge saw sustained or repeated activity during the prehistoric period, rather than a single isolated episode of use.