At Lislea in County Longford, on a gentle south-west-facing slope, lies a ringfort that has all but vanished into the land around it, leaving no trace visible at ground level. A ringfort, in broad terms, is a roughly circular enclosure defined by an earthen bank and ditch, used as a farmstead and place of protection during the early medieval period in Ireland. Thousands survive across the country in varying states of preservation. This one, it seems, has not fared especially well.

The site appears on the 1837 edition of the Ordnance Survey six-inch map, marked as a circular enclosure and labelled simply "Fort", which tells us it was still recognisable to surveyors in the nineteenth century. By 1976, when a recorded inspection took place, what remained was a raised circular area of roughly forty metres in diameter, enclosed by a bank of earth and stone with an external fosse, the fosse being the ditch that typically ran around the outside of such an enclosure to reinforce the defensive effect of the bank. Even then, the original entrance could not be identified. Since that point, the monument has apparently become invisible at ground level entirely, absorbed back into the quiet agricultural landscape of south Longford.