Scorched material, visible where the stream bank has been cut away, marks the site of a fulacht fia, a type of prehistoric cooking site found in considerable numbers across Ireland. The name translates loosely from Irish as "cooking place of the wild men" or "cooking place of the deer", and the remains are typically a horseshoe-shaped mound of fire-cracked stones and charcoal-blackened soil, built up over repeated use across hundreds or even thousands of years. The standard interpretation is that water was heated by dropping stones, first fired in a hearth, into a trough or pit, allowing meat to be boiled without direct flame.

What makes the Ballynagree site quietly notable is not any singularity but the opposite: it sits immediately beside a second fulacht fiadh to the south-east, the two lying close enough together to suggest that this stretch of the stream was returned to again and again, perhaps because the water supply was reliable and the ground suitable. The burnt material still showing in the stream bank section is a reminder that these sites are not always buried tidily beneath the surface; erosion can expose the evidence, which is part of how they are so frequently identified across the Irish landscape. Cork alone contains an exceptionally high density of recorded examples.