The site is a cillín, the Irish term for an unconsecrated burial ground used historically for unbaptised infants, and occasionally for others who fell outside the boundaries of formal Catholic burial, such as suicides or strangers. These places exist in their hundreds across Ireland, many of them unmarked on any public map, occupying a particular and melancholy position in rural memory.

The enclosure at Sylaunnagran is roughly D-shaped, measuring approximately 24.5 metres along its longer axis, and is defined by an earthen bank with a fosse, a shallow ditch, running along both its inner and outer edges. This kind of enclosure formula, an earthen boundary with ditches on both sides, is found at a number of cillíní and may echo far older land-dividing traditions, though the graves themselves are the site's defining feature. Over two hundred set stones survive within the interior, a density that speaks to generations of quiet, informal use. Near the centre sits a low cairn of loose limestone pebbles, roughly two metres wide and just over two metres long, its function unspecified but its placement deliberate. Whether it predates the burials, marks an individual grave of some local significance, or served some other purpose is not recorded.