The Ordnance Survey's six-inch sheet from that year shows a large oval embanked enclosure, measuring roughly 35 to 40 metres north to south and 25 to 30 metres east to west, sitting at the break of a gentle slope with a stream running some 120 metres to the south-east. By the time later map editions were produced, it had vanished from the cartographic record entirely, and on the ground it has been levelled flat. Field fences now cross the site, and farm buildings occupy its northern end.

A rath, to use the Irish term, was typically an enclosed farmstead of the early medieval period, defined by one or more earthen banks and ditches and home to a family of some local standing. They are among the most common monument types in Ireland, numbering in the tens of thousands, yet a great many have been lost to precisely the kind of agricultural improvement that erased this one. What makes the Lislackagh example quietly notable is the completeness of its disappearance. There is no earthwork to visit, no raised ground to stand on, no visible trace of the bank that would once have defined the enclosure. The 1838 survey caught it at what was probably already a late stage, and nothing after that thought it worth recording.