It rises only about a quarter of a metre above the surrounding ground, and yet it is composed almost entirely of burnt material, the accumulated debris of repeated prehistoric cooking, or possibly bathing or industrial activity, carried out over generations. At its centre is a shallow hollow, roughly seven metres north to south and just over five metres east to west, which is the telltale signature of the trough that once sat at the heart of the whole operation.

A fulacht fia, sometimes called a burnt mound, is among the most common prehistoric monuments in Ireland, though that familiarity has done little to settle debates about what exactly they were used for. The basic principle is well understood: stones were heated in a fire, dropped into a water-filled trough, and the resulting heat used for cooking, textile processing, or bathing. The shattered, fire-cracked stones were raked out after use and piled nearby, and it is those accumulations of blackened, fragmented rock that form the distinctive horseshoe or oval mounds still visible across Irish farmland today. The Finnoo example was recorded and compiled by Denis Power, with notes uploaded in August 2011. The landowner noted that the mound had been reduced to its present modest height in the recent past, which means what survives is already a diminished version of the original accumulation. The overall footprint still measures roughly sixteen metres north to south and twelve and a half metres east to west, suggesting that before any disturbance took place, this was a substantial feature.

The site sits in low-lying, marshy ground, which is entirely typical for this class of monument. Prehistoric communities placed fulachta fia near reliable water sources, and boggy or waterlogged pasture often preserves the burnt material better than drier ground. Visitors to this part of County Limerick should be prepared for soft underfoot conditions and should look for the slight rise in the field surface, easily missed given how much the mound has been reduced. The central hollow, though shallow at around thirty-five centimetres deep, remains visible and gives the mound its characteristic shape.