Known locally as Lurgan Cairn, this enigmatic feature was first noted by Killanin and Duignan in the 1960s as a possible chambered cairn, though its true nature remains frustratingly unclear. The mound now serves as a base for an Ordnance Survey trigonometrical pillar, but what lies beneath the accumulated earth and vegetation is anyone’s guess; it could be a prehistoric burial chamber, or perhaps something else entirely.

The cairn doesn’t stand alone on this hilltop. It sits towards the northeastern edge of a smaller circular enclosure, about 35 metres in diameter and defined by an earthen bank. Both of these features are encompassed by something far more impressive: a massive D-shaped enclosure that stretches approximately 340 metres from north to south and 200 metres from east to west. The eastern boundary takes advantage of the natural topography, using a steep escarpment as a ready-made defensive wall, whilst the remaining perimeter consists of the tumbled remains of what was once a substantial stone wall curving around the crown of the hill.

Archaeological opinions differ on what this sprawling hilltop complex represents. Most scholars interpret it as a hillfort, presumably dating to the Iron Age when such defensive structures were common across Ireland. However, some researchers have suggested a more ancient origin, proposing it might be a Neolithic enclosure that would place it thousands of years earlier. The site has attracted scholarly attention since at least the 1940s, with various surveys and studies attempting to unlock its secrets, though definitive answers remain elusive.