That mound was a fulacht fia, a type of prehistoric cooking site found in great numbers across Ireland, typically identified by their distinctive horseshoe or kidney shape and the presence of fire-cracked stones. They are thought to have functioned by heating stones in a fire and dropping them into a water-filled trough to bring it to the boil, a process that leaves behind a characteristic burnt-stone mound. This particular example no longer exists in any physical sense.

According to local information recorded by Walsh in 1985, the mound was levelled around 1973 during drainage works on the surrounding land. The reclaimed marsh that once preserved it, the waterlogged, low-oxygen conditions that tend to keep such features intact for millennia, was itself the casualty of agricultural improvement. By the time the site was formally documented in the Archaeological Inventory of County Cork in 1994, there was already no visible surface trace remaining. What survives is essentially a cartographic ghost: a hachured outline on a six-inch Ordnance Survey sheet, and a note in the local record.

There is nothing to see at Ballintannig today, and that absence is itself the point. The fulacht fia was common enough that thousands survive across the island, yet common enough also that individual examples could disappear in an afternoon's drainage work with barely a record made. This one was at least noticed on a map, and eventually given a number in a county inventory, which is more than can be said for others that vanished without any documentation at all.