This one, in the low-lying rough pasture of Knockballyfookeen in County Limerick, does almost the opposite. It exists, in practical terms, only as a ghost in a single aerial photograph, a faint subcircular cropmark visible from the air in 1986 and invisible in every subsequent image taken of the same ground. It does not appear on the Ordnance Survey's historic maps. It leaves no trace on modern orthophotos or satellite imagery. What makes it remarkable is precisely this quality of near-erasure, the fact that it is known at all only because a survey plane happened to pass over at the right angle, in the right season, when the buried geometry briefly expressed itself through differential grass growth.

A ring barrow is a prehistoric burial monument, typically a low central mound or flat area enclosed by a circular ditch and an outer bank, and they are found across Ireland in considerable numbers. This example was identified during the Bruff aerial photographic survey of 1986, recorded as reference Bruff 266, AP 4/3677, and compiled into the national monuments record by Alison McQueen and Vera Rahilly, with the record uploaded in October 2020. The site sits approximately 190 metres east of the townland boundary with Ballyhurst, in ground cut through by land drains and watercourses, which likely accounts for both its poor surface preservation and its intermittent cropmark visibility. It is not an isolated anomaly in the landscape: two other ring barrows lie within 125 metres, one to the south and one to the northwest, and a standing stone sits just 45 metres to the northeast, suggesting this quiet, waterlogged corner of Limerick was once a place of some ceremonial or funerary significance.

For anyone curious enough to seek it out, the site is in working farmland and there is nothing on the ground to indicate where the monument lies. The land drains and the generally marshy character of the pasture make the approach uneven. The aerial survey image, referenced as Bruff 266, remains the clearest evidence of the monument's form, and the national monuments record for this townland, which clusters several related sites nearby, gives the fullest picture of what survives in this part of south County Limerick. The standing stone to the northeast is the one element of the group likely to be visible on a visit, and that alone may reward the detour.