It is a fulacht fia, a type of prehistoric cooking site found in extraordinary numbers across Ireland, and one of the more persistent puzzles in Irish archaeology. The basic mechanism is well understood: a trough, usually dug into waterlogged ground or close to a stream, was filled with water, and stones heated in a nearby fire were dropped in to bring the water to a boil. The cracked and shattered stones, useless after a few heatings, were piled to the side, and over generations these discarded heaps built up into the horseshoe-shaped mounds that survive today.

Fulachtaí fia are among the most common prehistoric monuments on the island, with thousands recorded, yet their precise social function remains genuinely contested. Cooking is the most widely accepted explanation, and experimental archaeology has shown that the method works efficiently for boiling large joints of meat. Other theories, argued with varying degrees of conviction, include brewing, hide-working, and bathing. The Killulla example sits within a county that has no shortage of prehistoric activity, from the limestone pavements of the Burren with their portal tombs and ring forts to the damp marginal land further inland where fulachtaí fia tend to cluster near water sources. The specific details of this site, its dimensions, its precise condition, and any associated finds, are not yet in the public domain.