What makes the site at Glenastar particularly notable is not its size, which is modest, but the survival of a double-bank arrangement that gives a clearer sense of early medieval enclosure than a simpler, single-banked example would. Ringforts, known in Irish as raths, were the most common form of rural settlement in Ireland during the early medieval period, roughly the fifth to twelfth centuries. They served as enclosed farmsteads, the earthen banks and ditches marking status and providing a degree of security for livestock and family alike.

The enclosure here measures approximately 21 metres north to south and 22 metres east to west, making it a roughly circular space enclosed by two concentric earthen banks with a fosse, that is a ditch, running between them and a further fosse on the outer edge. The inner bank stands to an external height of around 1.1 metres for most of its circuit, while the outer bank is marginally more imposing at about 1.5 metres externally. Both banks show their most reduced profile at the south-southeast, where the inner bank grades down to a scarped edge and the outer barely registers at its interior face. Between the two banks, rather than a continuous ditch, much of the circuit is separated by a flat terrace that widens to around four metres at the south-southeast. The external fosse is traceable on the western and north-north-western arc. A field boundary recorded on the 1923 Ordnance Survey six-inch map as abutting the site at the north has since been removed, though another boundary still skirts the enclosure to the south. The site was compiled and documented by Denis Power.

The interior slopes gently downward toward the south-southeast and is used as rough grazing, which has kept the ground open enough for the earthworks to remain legible underfoot. The tree cover, while atmospheric, means that the banks are perhaps best appreciated on a winter visit when the canopy is bare and the low light catches the subtle changes in ground level. The fosse sections that survive are shallow, some barely 30 centimetres deep externally, so careful attention is needed to read the full plan of the site. Walking the outer circuit, particularly the south-western to north-eastern arc where the intervening ditch is most clearly defined, gives the best sense of the original layered defences.