It measures roughly five metres north to south, six metres east to west, and rises to about 0.9 metres. To a passing eye it might read as nothing more than a slight rise in the ground. What it actually represents is the accumulated debris of prehistoric cooking, a fulacht fia, one of the most common yet persistently enigmatic monument types in the Irish landscape.

A fulacht fia, sometimes called a burnt mound, is the remains of an ancient outdoor cooking site, typically Bronze Age in date. The method involved heating stones in a fire until they were intensely hot, then dropping them into a water-filled trough to bring it to a boil. The stones, cracked and shattered by the repeated thermal shock, were discarded to one side after use. Over generations of activity, these rejected fragments accumulated into the horseshoe-shaped or oval mounds that survive today across Ireland in their thousands. The Ballagh example is partially levelled and overgrown, but the burnt material that makes up its core is still legible as a distinct earthwork. What makes the site particularly interesting is its apparent company. A researcher named Bowman, writing in 1934, recorded what appears to be a cluster of five such monuments within the same townland, suggesting this stretch of north Cork was a focus of repeated or prolonged prehistoric activity rather than a single isolated event. The proximity of the mound to a stream is entirely typical; access to a reliable water source was a basic requirement of the whole process.