The mound measures roughly thirteen metres along its longer axis and rises to about one and a half metres at its highest point, with an opening nine metres wide facing north-west. A smaller spread of burnt material lies just to the south-west, suggesting either a secondary episode of activity or spillover from the main deposit.

This is a fulacht fia, a type of site found in enormous numbers across Ireland, particularly from the Bronze Age onward. The term is often translated loosely as "deer roast" or "cooking place of the Fianna", though the precise meaning has always been debated. The physical form is well understood: a trough, usually timber-lined, was dug close to a water source and filled with water, which was then heated by dropping fire-heated stones into it. The shattered, heat-fractured stones were raked out and discarded to the sides, gradually building up the characteristic horseshoe-shaped mound of dark, burnt material that survives so conspicuously in the field. Whether such sites were primarily for cooking, bathing, or some other communal activity remains an open question among archaeologists. What is not in question is how well they preserve: the burnt stone mounds are both distinctive and durable, and Ireland has more identified examples than almost anywhere else in Europe. The one at Brittas follows the classic pattern closely, positioned beside running water and retaining its open-fronted form, though some material has been removed from the centre at some point, which is not unusual given that the loose, dark fill has historically been attractive as garden mulch or soil amendment.