The ring-barrow at Kilduff, in County Limerick, belongs firmly to the second category. It does not appear on Ordnance Survey Ireland's historic maps at all, and by late 2018 it had slipped even from satellite view, gone to ground as thoroughly as it had been for most of recorded history.

A ring-barrow is a low circular burial mound of the prehistoric period, typically enclosed by a surrounding ditch and sometimes an outer bank, and usually associated with Bronze Age funerary practice. What makes the Kilduff example particularly interesting is how it came to be known at all. It was identified as a circular cropmark during the Bruff aerial photographic survey in 1986, catalogued as Bruff 159.2 (AP 4/3678). Cropmarks of this kind appear when buried features, such as the cut of an ancient ditch, affect the moisture and nutrients available to overlying vegetation, causing it to grow differently to the surrounding field. In aerial photographs, particularly during dry summers, these differences show up as ghostly rings or lines in grass or grain. The Kilduff barrow is one of a cluster of three such monuments in the area, recorded together as LI024-252, 253, and 254. It sits in low-lying pasture dissected by land drains and watercourses, roughly 110 metres northwest of the townland boundary with Garrison. The monument was still detectable in orthoimagery captured between 2005 and 2012 by OSi, and again in Digital Globe imagery from 2011 to 2015, but had become invisible by the time a Google Earth image was taken in November 2018.

For anyone hoping to visit, the honest account is that there is likely very little to see on the ground. The field is working agricultural pasture, and the monument's signature is essentially atmospheric rather than physical, residing in archives and aerial photographs rather than in any upstanding feature. The records were compiled by Alison McQueen and Vera Rahilly and uploaded in October 2020 as part of ongoing archaeological survey work in the region. Those with an interest in the site are best served by consulting the aerial survey image Bruff 159.2 alongside the OSi orthoimage record, where the circular form is at least intermittently legible. The fact that it vanished from view between one image set and the next is itself a reminder of how contingent the survival of such records can be, and how much of the Irish prehistoric landscape exists in this uncertain, flickering state.