Yet that is precisely the situation with a small ring-barrow in the flat pasture of Glenogra, County Limerick, a site that has spent decades flickering in and out of visibility without ever quite settling into the permanent record.

A ring-barrow is a burial mound of prehistoric date, typically consisting of a low central mound encircled by a ditch and sometimes an outer bank. They are found across Ireland and Britain and are generally associated with Bronze Age funerary practice, though the type persisted across a long span of prehistory. The Glenogra example was first formally identified during the Bruff aerial photographic survey of 1986, catalogued as Bruff 1000 (AP 4/3598), with an external diameter of approximately six metres, placing it at the more modest end of the scale. What makes it genuinely odd is its subsequent documentary history. It does not appear on Ordnance Survey Ireland historic maps at all. It is visible on OSi orthoimages captured between 2005 and 2012, then absent from Digital Globe imagery taken between 2011 and 2013. It reappears on a Google Earth image dated 25 March 2017, and is gone again by the time another image was captured on 28 June 2018. The record was compiled by Edmond O’Donovan and uploaded in October 2020. The site sits 134 metres southeast of the Morningstar River and the townland boundary with Mortgage, with Glenogra Castle lying roughly 60 metres to the west-northwest and a further enclosure about 185 metres to the south-southeast.

The intermittent visibility is almost certainly a matter of soil conditions, grass growth, and the angle and timing of overflights rather than any change to the monument itself. Crop and soil marks of this kind are most legible in dry summers when differential moisture above buried features draws contrasting patterns in vegetation. At ground level, a ring-barrow this size, only six metres across and presumably much reduced after millennia of agricultural activity, would be easy to walk past without noticing. The surrounding pasture is privately farmed, and there is no public amenity or signage attached to the site. Those with an interest in aerial archaeology or in the wider Glenogra landscape, which includes both the castle remains and the nearby enclosure, would find the area worth examining on georeferenced aerial image platforms before visiting, since the monument is far more legible from above than underfoot.