These are fulachta fiadh, a type of site found across Ireland and typically associated with Bronze Age cooking, though their precise function is still debated. The usual interpretation is that stones were heated in a fire, dropped into a water-filled trough to bring it to the boil, and used to cook meat. The troughs, usually timber-lined pits dug into the ground, and the discarded cracked and fire-shattered stones that accumulated around them, are what survive.

The two mounds at Ballynabarny were identified during testing carried out by Ruth Elliot in October 2001, ahead of construction work on the N11 between Newtownmountkennedy and Ballynabarny. Excavation followed in 2002. Both mounds sat on the highest part of the slope, between 105 and 110 metres above sea level, overlooking Rathnew. The southern mound was at least 13 metres in diameter and had one possible trough beneath it; the northern, slightly smaller at 10 metres across, had three probable troughs beneath it, with another probable trough and a small pit immediately beside it. The northern mound had also partially covered what appeared to be four agricultural furrows, with possible ard-marks, running parallel down the slope at intervals of 1.5 to 2 metres. An ard is a simple form of plough, and the faint scratches it leaves in subsoil can survive for millennia. One of the troughs had actually cut through one of these furrows, suggesting the farming activity predated at least part of the fulacht complex, or that the two were broadly contemporary. Several smaller features containing burnt material lay within 30 metres of the mounds, and a piece of pottery provisionally dated to the Bronze Age was recovered from one of them, lending support to a Bronze Age date for the whole group. Further up the slope, in a separate area to the west, a cluster of up to twelve small pits or post-holes of possible prehistoric date was also recorded, though no clear pattern could be established among them.