It does not look like much at first glance, but what it represents is one of the more intriguing puzzles in Irish prehistory. This is a fulacht fia, a type of ancient cooking site found in enormous numbers across Ireland, typically Bronze Age in date, and almost always positioned close to a water source. The usual interpretation is that stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil, with the discarded, shattered stones gradually accumulating into the characteristic horseshoe-shaped mound that survives today. The hollow at the centre of this one is that trough, or at least its ghost.

What makes the Ballyduane example worth pausing over is its scale. When Thomas Bowman recorded it in 1934, he noted it as exceptionally large, measuring fifty-seven feet in diameter and standing over seven feet high. By the time of more recent survey work, the mound had settled somewhat, measuring roughly twelve metres north to south and just under ten metres east to west, with a height of about 1.2 metres. That kind of shrinkage is not unusual over decades of agricultural pasture, but even at its current dimensions it remains a substantial presence in the landscape. Bowman's original figures put it well above the typical range for these sites, suggesting either a very long period of use or unusually intensive activity at this particular spot.