In a stretch of level pastureland in Caherbulligin, Co. Galway, the outline of a circular stone fort roughly 43 metres across persists not in its original drystone walling but in the gentle curve of a later field boundary. The fort itself has vanished above ground, yet a farmer drawing a property line at some point in the intervening centuries unknowingly followed the ghost of something far older, preserving its circumference almost by accident.

Locally the site is known as the Cave-Fort, a name recorded by Redington in 1916 and one that almost certainly refers to the souterrain concealed within the north-eastern quadrant of the interior. A souterrain is an underground stone-lined passage or chamber, typically associated with early medieval settlements in Ireland, and thought to have served for storage, refuge, or both. McCaffrey, writing in 1952, classified the site as a stone fort of the cashel type, a cashel being a ringfort defined by a drystone wall rather than an earthen bank. The entrance gap in the northern arc of the wall was recorded at roughly 1.5 metres wide. How much of the original structure was still visible to McCaffrey is unclear, but the process of disappearance was already well advanced by the time Redington noted the local name a generation earlier.

What survives today is primarily that curving field wall and, beneath the ground, the souterrain. The name Cave-Fort suggests the underground element was the more memorable feature to those living alongside it, which makes a certain sense: the stonework overhead dissolved into later construction, while the passage underfoot endured.