It measures roughly ten metres across and would be easy to miss entirely at ground level, yet from the air its outline becomes clear: a ring-ditch, that quiet category of prehistoric earthwork whose purpose archaeology has long debated but never quite settled.

Ring-ditches are typically interpreted as the eroded remains of round barrows, the circular burial mounds raised during the Bronze Age, though some may have served other ceremonial functions. What survives at ground level is usually little more than the ditch that once surrounded a central mound, the mound itself having been ploughed or weathered away over millennia. The example at Lacken sits within the basin of the River Sow, with a north-south stream running approximately 250 metres to the west. This kind of low-lying, well-watered ground was often favoured for prehistoric activity, and the placement on a slight slope would have given the site a modest prominence in the local landscape without requiring any great elevation. Its existence is known primarily through aerial photography, that particular method of discovery that has transformed understanding of Irish prehistory by revealing cropmarks and soil variations invisible from the surface.