It measures 42 metres across, and although its surface is now dense with thistles and encroaching blackthorn, hawthorn, and hazel, the structure beneath all that growth is remarkably intact. This is a ringfort, the kind of enclosed farmstead that was the dominant form of rural settlement in early medieval Ireland, typically dating from roughly the fifth to the twelfth century. What makes Derryronan quietly compelling is the layering of evidence it contains: not just the main enclosure, but the traces of habitation and defence within it, all in various states of legibility.

The raised platform is defined by an earthen scarp, in places still topped with remnants of a bank or wall. At the north-west, traces survive of a fosse, an encircling ditch, along with an external bank of earth and stone, though both are largely obscured by overgrowth. The stonework adds a further complication. Drystone facing appears on several sections of the scarp, including a stretch at the south to south-west standing around 1.5 metres high, and a freestanding drystone wall along the north to north-east arc that sits about two metres back from the top edge of the scarp. Whether this stonework is original to the ringfort or was added later when the site was absorbed into a network of agricultural field walls is genuinely unclear. The question is not merely academic: ringforts were routinely reused across the centuries, their banks convenient boundaries for later farmers. At the south-south-east, a broad gap about four metres wide in the scarp, with traces of stone facing on one side, may mark the position of the original entrance. In the northern half of the interior, a souterrain, an underground stone-lined passage typically used for storage or refuge, runs beneath the ground. A few metres to its south-east, a low circular platform has been identified as a possible house site, the faint remains of a structure that once stood at the heart of the enclosure.