Ploughed flat on its north-western side, that portion of the Oldgrange ringfort now lies invisible beneath tillage, while the south-eastern arc survives in pasture, heavily colonised by nettles, brambles, and dead wood so thick that the banks are effectively unreachable. What remains is enough to show the original shape: a roughly circular enclosure, recorded on the 1904 to 1905 edition of the Ordnance Survey six-inch map as approximately 36 metres north to south and 38 metres east to west, which is a fairly typical size for a rath of its kind.

A ringfort, or rath, is a circular earthen enclosure built during the early medieval period, roughly 500 to 1200 AD, most likely as a defended farmstead for a single family and their livestock. The bank at Oldgrange has been reduced largely to a scarp, a low sloping edge rather than a proper raised bank, measuring about 1.2 metres wide with an internal height of just 0.26 metres, though the exterior still drops a more significant 1.07 metres, suggesting the original ditch or outer face held its form rather better than the inner. There appear to be at least two breaks in the bank in the south-eastern quadrant, which may indicate original entrance points, though the scrub makes confident assessment difficult. Field boundaries that once ran to the north and north-west of the enclosure have also been removed, further altering the immediate landscape around it. A second ringfort sits roughly 250 metres to the north-west, a reminder that these structures were rarely isolated features but part of a lived-in, working countryside.