The ringfort at Allagesh in County Monaghan belongs to the second category. A rath, as this type of monument is commonly called, is a circular enclosure defined by an earthen bank and sometimes a surrounding ditch, typically dating from the early medieval period and used as a farmstead or place of habitation. The one at Allagesh sat on top of a short ridge running northeast to southwest, and when it was recorded in 1967 it still presented as a clearly legible circular grass-covered area, roughly 34 metres across at its widest. By 1995, it was gone.

The 1967 description is precise enough to conjure what had been there. The enclosing earthen bank, incorporated along much of its circuit into a later field boundary, stood to an external height of 1.3 metres on the northwest side, with a base width of 2.5 metres. On the southwest, the bank gave way to a simple scarp, around 2 metres wide and 0.45 metres high. No evidence was found of a fosse, the outer ditch that typically accompanies such earthworks, and no original entrance could be identified. Those absences are not unusual; many raths survive without a clearly legible fosse, and entrance gaps can close over with centuries of slippage and ploughing. What is unusual is the completeness of the subsequent loss. The Ordnance Survey Air Photography programme recorded its removal sometime before 1995, leaving the ridge at Allagesh with no surface trace of what had stood there for perhaps a thousand years.