It measures roughly fifteen metres along its longer axis and just over a metre in height, and it is made almost entirely of burnt and fire-cracked stone. This is a fulacht fia, a type of prehistoric cooking site found in enormous numbers across Ireland, more commonly recognised by its characteristic horseshoe or kidney shape. The rectangular form here is less typical, which makes this particular example a little harder to read at first glance.

Fulachtaí fia, the plural form, are generally understood to be Bronze Age in origin, though some may be earlier or later. The working principle was straightforward: a trough, usually timber-lined or cut into the ground near a water source, was filled with water, and stones heated in a fire were dropped in to bring the water to a boil. Over repeated use, the shattered, heat-spent stones accumulated into the mounds we see today. The proximity to a stream at Laharan fits this pattern precisely, since a reliable water supply was essential to the whole process. What was actually being cooked, or whether cooking was even the primary purpose, remains a matter of some debate among archaeologists; brewing, bathing, and textile processing have all been proposed as alternative or additional uses.