It is a fulacht fia, a type of prehistoric cooking site found in great numbers across Ireland, typically identified by the crescent or horseshoe-shaped mounds of fire-cracked stone that accumulate around a trough. The general method, as archaeologists understand it, involved heating stones in a fire and dropping them into a water-filled trough to bring the water to a boil, then using that heat for cooking, and possibly for other purposes such as textile preparation or bathing. The mound at Ballynatona is the physical residue of that repeated process: layer upon layer of burnt and shattered stone, discarded after use.

The mound measures roughly ten metres east to west and eight metres north to south, rising to about 1.2 metres in height. It sits on the western bank of a stream, which is entirely typical of the type; proximity to a reliable water source was a practical necessity for fulachta fia, and they cluster along watercourses and boggy ground throughout the Irish landscape. The site is overgrown now, its shape softened by vegetation, and the northern edge has suffered damage from machinery used during drainage work, a fate that has befallen many such monuments across the country as agricultural improvement has encroached on land that was once considered marginal or unproductive.