At Ballybetagh, near Glencullen Village in south County Dublin, a roughly circular enclosure some twenty-five metres in diameter lies beneath improved pasture at the foot of Newtown Mountain, leaving no trace whatsoever at ground level. The shape of it survives only in cartography and the written record, a presence that exists more on paper than in the soil.

The enclosure appears on the Ordnance Survey six-inch map of 1843, recorded with enough clarity to suggest it was still legible in the landscape at that time, or at least within living memory of the surveyors' informants. It may well be one of the circular features noted in the OS Letters of 1837, a series of detailed topographical and antiquarian observations compiled by the Ordnance Survey during its mapping of Ireland, and later cited by scholar Michael Herity in 2001. Enclosures of this kind, sometimes referred to as ringforts when they served as enclosed farmsteads in the early medieval period, are among the most common archaeological monument types in Ireland, yet their very familiarity has not protected them from agricultural improvement, drainage, and gradual erasure. What survives at Ballybetagh is, in a sense, the ghost of a monument rather than the monument itself.

The site sits in agricultural land near Glencullen, a village in the Dublin Mountains that is accessible from the south city via a winding upland road. Because the enclosure is not visible at ground level, there is little to see on a visit in the conventional sense. The value of coming here is more contemplative than archaeological; knowing that something once stood, was mapped, was noted by nineteenth-century scholars, and has since slipped below the surface of the pasture gives the ordinary-looking field an unexpected quality. The research was compiled by Geraldine Stout and Padraig Clancy, with the record last updated in April 2018, and it stands as a small example of how much of Ireland's ancient landscape now exists only in archive form, documented but invisible.