Look more carefully and the shape resolves itself: an earthen bank, overgrown but intact, running around a space some thirty-three metres across from east to west and thirty-one from north to south. The bank itself is between four and five metres wide, and though it rises less than a metre and a quarter on its outer face, that modest height is enough to suggest an enclosure built with deliberate purpose rather than accumulated by accident. A fosse, the ditch that would originally have reinforced the bank's defensive or demarcating function, can still be traced on the east-south-east side, not as an obvious hollow but as a band of rushes roughly two and a half metres wide, wet ground betraying where the old cut still influences drainage. An entrance gap of three and a half metres survives at the south-south-east.

What makes this particular enclosure worth pausing over is its proximity to a much larger earthwork. Roughly fifty metres to the north lies the southern bank of the Doon of Drumsna, a linear earthwork that runs across the landscape on a considerable scale. Linear earthworks of this kind, sometimes called black pigs' dykes or similar names in Irish tradition, are among the more enigmatic monuments of early medieval or Iron Age Ireland; they appear to have marked territorial boundaries or controlled movement across the land rather than enclosing a settlement. The embanked enclosure at Lackagh sits in close relationship to that larger structure, its own bank even incorporated into a field boundary running north-north-west to east, which suggests the enclosure was considered a fixed point in the landscape long enough for later land divisions to use it as a convenient anchor. Whether the two monuments were contemporary or simply accumulated near one another over time is not something the earthworks alone can answer.