It measures roughly twenty metres north to south and sixteen metres east to west, and it has been there, in one form or another, since the Bronze Age. It is a fulacht fia, a type of ancient cooking or processing site found in enormous numbers across Ireland, typically beside a water source. The characteristic mound is made up of burnt and shattered stone, the accumulated debris of thousands of heating cycles in which rocks were fired and dropped into water-filled troughs to bring the liquid to a boil.

Fulachtaí fia are among the most common prehistoric monuments in the Irish landscape, yet the one near Killeagh is notable simply for its survival in cultivated, reclaimed ground, where such features are frequently levelled or disturbed by agricultural work. The mound's low profile and oval shape are typical of the type. What purpose these sites served beyond basic cooking has been debated, with suggestions ranging from textile processing to brewing, though no consensus has settled the question. What is not in doubt is the sheer industriousness they represent: the same method, repeated across millennia, leaving a gentle swell in the earth that tillage has not yet erased.