What survives at Fallathurteen is barely there at all: a slightly raised oval of ground, some thirty-two metres across its longest axis and twenty metres at its widest, enclosed by a low bank of earth and stone that at its most visible rises only thirty centimetres above the interior. There is no visible fosse, the defensive ditch that typically accompanies such enclosures, and no legible entrance survives. On casual inspection, this could pass for a natural undulation in the field.

The site is a cashel, a form of ringfort defined by its use of stone rather than earthen ramparts. Ringforts, built predominantly during the early medieval period in Ireland, served as enclosed farmsteads, their banks and ditches marking out a household's territory and offering a degree of protection for people and livestock. At Fallathurteen, the enclosing bank is composed largely of limestone rubble, which fits the local geology of County Sligo, where limestone lies close to the surface across much of the landscape. What makes this particular example quietly melancholy is how thoroughly it has been absorbed into the working countryside around it. Along the north-east to south-east arc, the original bank has been folded into a drystone field wall, the old fabric of the monument repurposed for an entirely practical boundary. Large limestone boulders sit at the base of that wall and reappear intermittently around the south-west to north-west stretch of the bank, suggesting the original structure was once considerably more substantial before successive generations of farmers found its stone more useful elsewhere.

The interior slopes gently toward the south-east, and it is this slight tilt, combined with the barely perceptible rise of the surrounding bank, that gives the site away once you know what you are looking for. The oval form, even at its diminished height, holds its shape against the surrounding pasture if the light falls at a low angle, early morning or late afternoon being the more revealing times.