But the slight depression on the summit hints at a longer and more complicated story. A ring barrow is a type of prehistoric burial monument, typically a central mound enclosed by a circular ditch and an outer bank; the form is found across Ireland and Britain, generally associated with Bronze Age funerary practice. At Archerstown, the overall diameter of the monument, taking in the mound, ditch, and bank, is recorded at around 22.5 metres, though the central mound itself measures roughly 9 metres north to south and just over 8 metres east to west, rising to only 0.8 metres at its highest point. Despite its modest appearance, probing of the mound revealed that it contains a substantial quantity of stone beneath its earthen surface.

When a survey was carried out in 1973, the V-shaped fosse, a term for a defensive or ceremonial ditch, and the outer bank were described as being in considerably better shape than they are today. By the time David McGuinness surveyed the site in 2015, much of the edge had been broken up by livestock, and the ditch and bank survived only partially on the southern and south-western sides. Two unusual tongue-like projections extend from the east and west sides of the mound; whether these are original features of the monument or later additions is not known. A depression in the upper surface of the mound may point to the collapse of a cist, a small stone-lined burial chamber, or equally to disturbance by people hoping to find something more tangible than prehistory. The monument has held a preservation order since 1977. About 750 metres to the north-west lies a graveyard and ruined medieval church, which the archaeologist Leo Swan identified in 1988 as an early medieval ecclesiastical site, noting that the shape of the graveyard suggested it had once been enclosed by a curvilinear vallum, the boundary that typically defined an early Irish monastic settlement. The proximity of a prehistoric burial mound and an early medieval religious enclosure in the same stretch of Westmeath landscape is not coincidental; early Christian communities in Ireland frequently established themselves near older sacred or ceremonial sites.