It measures about six metres across in each direction, unremarkable to the casual eye, but it belongs to one of the most widespread and persistently puzzling categories of monument in the Irish countryside.

A fulacht fia is a type of prehistoric cooking site, found in their thousands across Ireland, typically dating from the Bronze Age. The general principle involves heating stones in a fire, dropping them into a water-filled trough to bring it to a boil, and cooking meat or other food in the heated water. The spent, cracked stones were raked out and discarded, and over centuries of use these spoil heaps accumulated into the characteristic horseshoe or kidney-shaped mounds that survive today. The example at Garranenageevoge fits this pattern well: its boggy setting is typical, since fulachta fiadh tend to cluster near water sources or in low-lying, wet ground where water was readily available. The mound itself is composed of that familiar burnt material, the shattered debris of repeated heating and cooling.