This is a fulacht fia, a type of prehistoric cooking site found in considerable numbers across Ireland, typically identified by their characteristic crescent-shaped spreads of fire-cracked stone and charcoal-blackened earth. The working theory behind most of them is straightforward enough: stones were heated in a fire, then dropped into a water-filled trough to bring it to a boil, the cracked and spent stones accumulating into the distinctive mound that survives today.

The Lissanisky example measures roughly 19 metres along its northwest to southeast axis and just over 13 metres across the other way, with its opening facing northwest. A smaller, circular mound of burnt material sits at the western side of that opening, an arrangement that hints at repeated, organised use of the site rather than a single episode of activity. The location follows a pattern well established for this monument type: marshy ground beside a stream, where water was readily available and the soft earth could be easily worked. Fulachtaí fia are generally dated to the Bronze Age, though some have produced earlier or later dates, and their precise function remains a matter of ongoing discussion among archaeologists, with cooking, bathing, and textile processing all proposed at various sites across the country.