It measures nine metres across in both directions and rises to almost two metres, which makes it a substantial presence in the landscape, even if its significance is easy to miss without context. The opening of the mound faces south, and its western edge has been worn down over time.

This is a fulacht fia, a type of prehistoric cooking site found in considerable numbers across Ireland, particularly in low-lying or waterside locations. The typical arrangement involved a trough dug near a water source, which was filled and then heated by dropping fire-cracked stones into it; the discarded burnt stones accumulated over repeated use into the distinctive mounded form that survives today. The mounds are most commonly dated to the Bronze Age, roughly between 1500 and 500 BC, though some sites have yielded earlier or later dates. The example at Derrylough sits on the east bank of a river, which fits the pattern well; proximity to running water was fundamental to how these sites functioned. The surrounding blanket bog, which is characteristic of upland Kerry terrain, has helped preserve the mound by sealing it from disturbance, though the western side has seen some erosion or degradation.