What makes the site at Coolawaleen quietly puzzling is how it has shifted shape across successive maps: the Ordnance Survey recorded it as a circular enclosure in 1842, yet by 1905 and again in 1936 the same feature appeared as a subrectangular form, roughly 60 metres east to west and 48 metres north to south, with rounded corners and a convex eastern end. Whether that apparent transformation reflects genuine reinterpretation of the earthwork, different surveyors reading the same ground differently, or actual change to the structure itself over those intervening decades, is not entirely clear.

By the time a researcher named Bowman recorded it in 1934, the site was described as a single-ramparted fort of about 62 yards in diameter on land belonging to a M. O'Connell, with an enclosing bank roughly four feet high and an external fosse, or defensive ditch, about four feet deep and five feet wide. A fosse is a ditch dug around the perimeter of a ringfort or similar enclosure, often forming part of the same construction event as the bank. That outer ditch, now 2.2 metres wide where it can be measured, survives as little more than a differential growth pattern visible in the grass across the northern to west-south-western arc of the site. Aerial photography from 1975 showed the interior under cultivation and the enclosing elements already overgrown, while a 1984 photograph captured the bank and fosse as cropmarks, the buried archaeology betraying itself through variations in how the crops above it grow. A possible souterrain, an underground stone-lined passage associated with early medieval settlement, has also been identified within the interior, adding another layer to what the ploughed field conceals.