On an 1842 Ordnance Survey sheet, the enclosure here appears as a six-sided figure sitting neatly against the southern edge of a townland boundary. By the time the surveyors returned in 1905 and again in 1937, they were recording something that looked quite different: a D-shaped enclosure, roughly thirty metres across, with the straight side formed by the townland boundary itself. The shape had apparently changed, or perhaps the earlier surveyor interpreted the outline differently. Either way, the discrepancy quietly raises the question of how much these features shifted, were altered, or were simply read differently by different eyes across the span of a century.

The enclosure at Ballybahallagh sits in pasture on a north-east-facing slope above a stream, and it has been substantially levelled over time. What remains is a D-shaped area, the straight northern side measuring around twenty-seven metres east to west, with the curved portion projecting about twenty-one metres southward. A low grass-covered rise, barely thirty centimetres above the interior at its highest, traces the arc from north-east around to south-south-west. Outside this, a shallow fosse, a ditch that would once have reinforced the boundary of the enclosure, runs from the north-east around to the north-west, though it now survives to a depth of only about twenty-five centimetres. The most pronounced earthwork is on the northern side, where a scarp drops 1.25 metres down to a farm trackway, and the same scarp continues falling toward the stream beyond. The interior itself appears slightly raised and tilts gently northward. Enclosures of this kind are common across the Irish landscape and are often interpreted as the remains of early medieval farmsteads, places where a family and their livestock were once enclosed within an earthen bank or stone wall, though the function of any individual example is rarely certain without excavation.