At Lyre in north Cork, a roughly circular enclosure once occupied a north-facing elevated position above the Glen River, its builders apparently content to let a straight-sided cliff face do much of the defensive work along the north-eastern edge. Two curving banks completed the circuit where the natural drop was insufficient. The whole structure measured around thirty metres in diameter, small enough to suggest a single defended homestead rather than a communal stronghold, and positioned to command the river valley below.

The fort appeared on Ordnance Survey six-inch maps in both 1904 and 1937, rendered in the hachured style surveyors used to indicate earthwork banks and ditches. By the time of the 1937 edition something had already shifted: the interior was recorded not as open ground but as a raised platform, suggesting the enclosure's internal features had been altered or were being read differently. Gravel quarrying eventually finished the job entirely, and no visible remains survive above ground today. The quarrying did, however, produce one unexpected disclosure. Workers uncovered a souterrain, an underground stone-lined passage of the kind often associated with early medieval ringforts and used for storage or refuge. Investigating that souterrain in 1968, O'Kelly and Shee recorded what was then still partially legible: part of the bank, some of the ditch, and a stretch of the counter-scarp bank on the uphill southern side, the earthwork elements that would have defined the landward approach to the fort before machinery removed them.

What makes the site quietly instructive is the particular combination of natural topography and constructed defences. The cliff edge was not incidental; it was load-bearing to the whole design, reducing the amount of labour needed to bank and ditch the perimeter. That strategy appears repeatedly in Irish prehistoric and early medieval fortification, but here the geology did the builders an unusually generous favour, and the Glen River below would have provided both a visual barrier and a practical resource. The gravel quarry has since erased all of that from the landscape.