Stretching roughly 1.2 kilometres from north to south and about 200 metres wide, this multiphase field system runs between Cappanawalla Hill and Gleninagh Mountain, connecting and overlying a series of older structures in a way that suggests it was not built in any single moment but accumulated across generations, perhaps across entire eras.

The field system anchors itself at its northern extent around an enclosure and at its southern end around a cashel, which is a type of stone-walled circular fort typically associated with early medieval settlement in Ireland. Between these two points, small irregularly shaped fields are defined by low mound walls, two of which cross the interior on roughly east-west alignments. These walls are modest in scale, between 2.5 metres wide and rarely more than half a metre high, but their construction method is the significant detail. Mound walls of this kind, built from accumulated soil and stone rather than dry-laid upright courses, are generally considered a marker of prehistoric field boundaries, placing this system potentially well before the early medieval period that the cashel might suggest. Researchers including Plunket Dillon in 1985 and subsequent work by Jones, Carey, and Hennigar have drawn attention to this likelihood. Around 100 metres northeast of the southern cashel, three further enclosures and a hut site add further layers to the picture. Two comparable field systems of similar antiquity exist elsewhere in Rathborney Valley, one in the northwest corner and one along the eastern side, each also incorporating enclosures or ringforts. Taken together, they may once have formed a single interconnected agricultural landscape across the valley floor.

Much of that broader system is now invisible. Between the first and second editions of the Ordnance Survey six-inch maps, published in 1842 and 1915 respectively, the valley's fields were substantially cleared and reorganised. Strip fields introduced after 1915 erased whatever surface evidence once connected these outlying systems to one another. What survives in the northeast corner of Rathborney Valley is therefore not simply old; it is what remained when the rest was swept away.