It runs for roughly 35 metres along a northeast-to-southwest axis, tucked against the foot of a north-northwest facing slope at Ballymartin in County Limerick. Its inner scarp-edge rises to just over three metres on the southern side, and an earthen field bank, standing about two metres high, defines its northern edge. Neither feature is immediately legible in the landscape: the bank is masked by vegetation, and the ditch itself is so thoroughly clogged with organic material that its original depth and profile are difficult to read. What survives is more impression than monument, the kind of earthwork that rewards patience over spectacle.

The site was recorded and compiled by Denis Power and uploaded to the national record in August 2011. Its designation as a dam, in the archaeological inventory sense, points toward a probable drainage function rather than anything more dramatic. The position of the feature is telling: set into the flood plain of the Shannon, it would have sat in a landscape perpetually negotiating with water. The ditch and accompanying bank are most likely the remnants of a drainage or water-management system, engineered to manage the seasonal behaviour of the nearby river and keep adjacent land workable. Earthworks of this kind, though unglamorous, were once critical infrastructure across lowland Ireland, where the difference between productive pasture and waterlogged ground often came down to the maintenance of features exactly like this one.

Access to this part of County Limerick is easiest by road, though the wooded and low-lying terrain around the site means conditions underfoot can be soft, particularly after wet weather. The earthen bank, smothered in vegetation, blends into the surrounding woodland in a way that makes it easy to overlook unless you are specifically looking for a subtle change in ground level. The ditch running beside it is the more legible of the two features, though the organic debris filling it has softened its edges considerably over time. Late autumn or winter, when leaf cover has thinned, is likely the clearest season for making sense of the topography.