It is a fulacht fia, a type of prehistoric cooking site found in enormous numbers across Ireland, typically consisting of a horseshoe-shaped mound of fire-cracked stones beside a trough and a water source. At Ballinphellic, the mound that once marked this site is no longer visible at the surface. The area is subject to flooding, and the soggy, shifting ground has swallowed whatever remained above ground level.

What we know of the site's existence comes largely from a 1940 Ordnance Survey six-inch map, which recorded a mound at this location. Fulachtaí fia, the plural form, are generally dated to the Bronze Age, though some examples extend into the early medieval period. The working theory behind most of them is practical rather than ceremonial: stones were heated in a fire, dropped into a water-filled trough to bring it to a boil, and used to cook meat or, as some researchers have argued, for bathing or textile processing. The burnt and shattered stones were then piled to the side, forming the characteristic mound. At Ballinphellic, that mound is now gone from view, leaving only its map notation as evidence.

The site sits in ground that floods regularly, which is not unusual for fulachtaí fia. Their builders almost always chose low-lying spots close to streams or springs, which made the whole operation practical but also ensured that, over millennia, many such sites have been obscured by peat growth, alluvial deposit, or simple waterlogging. At Ballinphellic, the combination of marshy terrain and seasonal flooding means there is nothing for a visitor to see today, the archaeology existing now as a cartographic ghost rather than a physical presence.