Visible only from the air, a D-shaped outline roughly sixty metres across reveals itself through differential crop growth, a phenomenon known as a cropmark, where buried ditches or banks cause the vegetation above them to grow at a slightly different rate, betraying the geometry of whatever lies beneath. The feature at Ballyharty is defined by a single fosse, an enclosing ditch, and its D-shaped plan raises the question of what it once contained or demarcated.

The site sits on level ground approximately 150 metres north-east of what was once the shoreline of Ballyteige Lough, a body of water whose original extent is recorded on the Ordnance Survey six-inch map of 1839. That same shoreline appears in a comparable position on the Down Survey, the ambitious mid-seventeenth-century mapping project carried out between 1656 and 1658 under William Petty, which aimed to document land ownership across Ireland following the Cromwellian confiscations. The consistency between these two maps, separated by nearly two centuries, suggests the lough's margin was relatively stable over that period, and that this enclosure was always set back a little from the water's edge. Whether the feature is a genuine early enclosure of the kind associated with settlement or ritual, or simply the ghost of an old field boundary incorporating a north-east to south-west bank along its north-western side, remains an open question.