It measures roughly ten metres along its longest axis and rises less than a metre from the surrounding earth, its sod-covered surface concealing a fill of shattered sandstone set in dark, scorched soil. That combination of fractured stone and blackened earth is the tell-tale signature of a fulacht fia, a type of ancient cooking site found widely across Ireland, typically dating from the Bronze Age. The accepted theory holds that stones were heated in a fire and then dropped into a water-filled trough, bringing the water to boiling point quickly enough to cook meat. Repeated heating and sudden cooling caused the stones to crack and splinter, and the discarded fragments accumulated over time into exactly the kind of horseshoe or oval mound visible here.

The wet, boggy ground around the site is not incidental. Fulachtaí fia are almost always found near a reliable water source, whether a stream, a spring, or simply an area where the water table sits close to the surface, and the marshy pasture at Spring Garden would have provided that in abundance. The mound sits roughly ten metres north-east of a separate enclosure, suggesting this part of the landscape saw repeated or sustained use over time, though the precise relationship between the two features remains unrecorded. The shattered sandstone within the mound points to locally sourced material, shaped by the same cycle of heating and fracture that produced similar monuments across the country in their thousands.