This one made itself known only from the air, and has since all but vanished again. On the demesne lands associated with Ryves Castle in County Limerick, an earthwork of uncertain purpose and age survives not as a visible ridge or hollow in the ground, but as a ghost in the landscape, something that appears in one photograph and disappears from another taken seventeen years later.

The site sits within a modern forestry plantation, immediately south of a watercourse, roughly 400 metres northeast of Ryves Castle itself. A fosse, meaning a defensive or boundary ditch dug into the earth, once defined an irregular enclosed area measuring approximately 60 metres northwest to southeast and 30 metres north to south. It does not appear on any Ordnance Survey Ireland historic mapping, which suggests it was either overlooked during the surveys of the nineteenth and early twentieth centuries, or was already too faint to register. What brought it to light was an oblique aerial photograph, reference ASIAP (342) 11, taken on 5 January 2003, which captured a curvilinear cropmark, the kind of faint discolouration in vegetation that betrays buried features beneath. A Google Earth orthoimage from May 2002 confirmed the enclosed shape. By September 2019, a later orthoimage showed no surface remains at all. The record was compiled by Martin Fitzpatrick and uploaded to the national monuments database in August 2021.

Because the earthwork has left no visible trace above ground, there is little to see on a visit in the conventional sense. The forestry plantation itself limits access, and the site is on private demesne land. What the record does offer, for those interested in landscape archaeology, is a reminder of how much survives only in the brief window between one aerial survey and the next, and how thoroughly plantation forestry can mask and eventually obliterate earthworks that were already marginal. Anyone researching the wider landscape around Ryves Castle would find the aerial photograph reference a useful starting point for understanding what the demesne may once have contained beyond its surviving built structures.