No earthwork breaks the surface, no stone protrudes from the grass, and the Ordnance Survey's historic maps record nothing at all. The only way to see this enclosure is from the air, where the buried archaeology betrays itself through differential crop growth, the slightly parched or slightly lush lines of vegetation that archaeologists call a cropmark. The enclosure at Ballincolloo is one of those places that exists, clearly and measurably, yet remains almost entirely invisible at ground level.

The site came to light in November 1984, when aerial photographs taken during survey work for the Bórd Gáis Éireann Curraleigh West-to-Limerick gas pipeline captured something unexpected in the fields below. Examination of those photographs, catalogued as BGE 1/50000 2552, revealed a roughly circular cropmark measuring approximately 22 metres north to south and 30 metres east to west, large enough to suggest a substantial enclosed space of the kind commonly associated with prehistoric or early medieval activity. A further set of aerial photographs, taken by the Archaeological Survey of Ireland in January 2003 and recorded as ASIAP 344/24, confirmed the monument's presence, as did orthophotography gathered between 2005 and 2012 and imagery from Google Earth. What all of these images share is the additional detail of a linear cropmark running east to west, cutting across the circular form at both its northern and southern edges, a feature that complicates any straightforward reading of the site. Whether that linear mark represents a later boundary, a field system, or something else entirely is not yet resolved. A possible barrow, a type of burial mound, has also been recorded approximately 110 metres to the southeast, catalogued separately as LI040-060, which hints that the area may have held significance across a long period. The enclosure itself sits around 110 metres east of the townland boundary with Tankardstown. The record was compiled by Fiona Rooney and uploaded to the national monuments database in April 2021.

There is nothing to see here in the conventional sense, and that is rather the point. The site sits on private agricultural land and is not accessible to visitors, nor does it present any surface feature that would reward a visit. What it offers instead is a useful reminder of how much of Ireland's archaeological landscape survives below the plough line, legible only in certain light, in certain seasons, when crops are under stress and the buried past briefly writes itself on the surface.