Not just the field boundary that a farmer has built into the northern arc of an ancient earthwork, but the boundary between two townlands, Lacka and Cahirduff, which runs precisely along the northern edge of a ringfort that was already old when anyone thought to draw such lines. That doubling up of function, early medieval enclosure becoming administrative limit becoming agricultural wall, is quietly telling about how Ireland's landscape accumulates meaning without ever quite announcing it.

A ringfort, or rath, is an enclosed farmstead of the early medieval period, typically a circular or oval area ringed by one or more earthen banks and ditches, used as a defended homestead rather than a military fortification. This example in the townland of Lacka, in the barony of Pubblebrien, sits on a gentle north-west-facing slope, pasture to its south, tillage to its north. It appears on the 1897 edition of the Ordnance Survey 25-inch map as an oval earthwork measuring roughly 60 metres on a north-west to south-east axis and 47 metres across. When the Archaeological Survey of Ireland examined it in 2007, the visible remains had contracted considerably, with a surviving semicircular area measuring approximately 30 metres by 16 metres. The enclosing bank, where it can still be read, is nearly 6.7 metres wide and stands up to 2.45 metres in external height. The fosse, the ditch that originally ran outside the bank, is about 5.85 metres wide and just over a metre deep in places, though it has been re-cut at some point to serve as a field drain, which is a common enough fate. A second enclosure lies about 75 metres to the south-east, suggesting this was once a busier corner of the landscape than it appears today.

The monument does not announce itself clearly on the ground. Much of the northern and western circuit has been absorbed into a field boundary, and the southern and eastern arc survives mainly as a cropmark, visible on aerial imagery from the 2005 to 2012 Ordnance Survey orthoimages and confirmed again on a Google Earth image from June 2018. That kind of partial survival, part earthwork, part cropmark, part repurposed wall, is worth understanding before a visit, since the eye needs to be trained on boundaries and slight rises rather than on any obvious mound or enclosure. The survey work, compiled by Alison McQueen and Vera Rahilly and uploaded to the record in October 2020, includes sketch plans and cross-sections that give a clearer sense of the original form than a ground-level inspection alone would allow.