The mound is easy to miss, rising only about 0.4 metres above the pasture and covered in sod, but its shape and setting are the giveaway. This is a fulacht fia, a type of prehistoric cooking site found in great numbers across Ireland, typically identified by the characteristic crescent or horseshoe form created by the gradual accumulation of fire-cracked and discarded stones.

The way a fulacht fia worked was straightforward: stones were heated in a fire, then dropped into a water-filled trough to bring the water rapidly to a boil, allowing meat to be cooked. Over time, the shattered, heat-spent stones were piled to the sides, eventually forming the distinctive mound shape that survives in the landscape today. At Breaghwy, a depression about five metres wide sits between the arms of the mound at the south-west end, which may mark where the trough once was. The mound measures roughly 15.5 metres north to south and 8.5 metres east to west, placing it well within the normal size range for such sites. The proximity to a natural spring would have been deliberate; a reliable water source was essential to the whole operation. Within about ninety metres to the north-west, there is also a rath, a type of enclosed farmstead typical of early medieval Ireland, consisting of a circular area bounded by an earthen bank or banks. The two monuments are not necessarily contemporary, but their closeness in this quiet corner of Mayo is a reminder of how densely this landscape was once used.