Not demolished, not built over, simply absorbed back into the landscape until nothing remains to catch the eye at ground level. That invisibility is, in its own quiet way, rather remarkable for a class of monument that numbers in the thousands across Ireland and usually announces itself as a clear circular earthwork rising from surrounding fields.

A rath, the earthen variety of ringfort, was typically the enclosed homestead of an early medieval farming family, its interior ringed by a bank and an outer ditch known as a fosse. The Lislea example was substantial enough, measuring roughly 27 metres east to west and 25 metres north to south, and it was clearly recognisable in the nineteenth century, appearing on the Ordnance Survey Fair Plan and on the 1837 edition of the six-inch map with the label 'Fort'. By the time a survey team visited in 1976, what remained was a raised subcircular area enclosed by only fragmentary traces of a low bank of earth and stone. There was no surviving fosse, and the original entrance had left no discernible trace. Just inside the interior, slightly east of centre, surveyors noted the remains of a possible house site, which would fit the domestic character typical of a rath. Whether the bank was deliberately levelled over generations of ploughing, or simply weathered down into the soft pasture around it, is not recorded.

The 1837 mapping is a useful reminder of how much can change in under two centuries of agricultural land use. What the Ordnance Survey cartographers recorded clearly enough to name and outline is now, by most practical measures, gone.