Located about 135 metres northeast of the Protestant church, this circular, flat-topped enclosure measured roughly 25 metres in diameter and rose some 2.4 metres above the surrounding landscape. When it was levelled around 1840, workers made a grim discovery: five cart loads of human bones were removed from the site, suggesting this was far more than a simple defensive structure.

The monument’s history is one of constant transformation. After its initial levelling in 1804, a school house was built on the spot, which was later knocked down and replaced by a handball alley and CYMS building, now serving as a snooker club. Historical records offer tantalising clues about what this earthwork might have been. The antiquarian Carrigan believed the abundance of human remains pointed to an ancient churchyard, noting that ‘Rath Domhnaigh’ translates to ‘the Rath of the Domhnach or Church’. This would place it within the graveyard that once enclosed Rathdowney’s medieval church.

Perhaps most intriguingly, this could be the site of a thirteenth-century castle built by Adam de Hereford between 1207 and 1213. Historical documents record that de Hereford was granted ‘the tuath of Mamocle in which his castle of Radouney stands’, though the exact location of this castle has long been debated. Some scholars connect it to references in the Ordnance Survey letters about a royal palace or castle called Rath Bacain that was ‘erected from the foundation’ during this period. Whether it served as a ringwork castle, an ancient church site, or both at different times, this lost monument represents layers of Rathdowney’s medieval past, now buried beneath modern buildings and local memory.