No wall, no bank, no obvious earthwork marks it out on the ground. What gives it away is a fosse, a wide ditch that once defined its boundary, now pressed flat by centuries of drainage and agriculture, but still legible as a faint shadow from the air.

The site was identified not through excavation or fieldwork in the conventional sense, but through satellite imagery. Google Earth orthophotos, which are overhead images corrected for the distortion caused by terrain, revealed the circular outline in the poorly drained grassland. Soil that has been waterlogged and then reclaimed tends to preserve these ghostly traces longer than drier ground; differences in moisture, buried ditches, and disturbed subsoil all show up as tonal variations in aerial photography. The enclosure at Lisnabin measures approximately 107 metres on its north to south axis, which puts it firmly in the category of a large enclosure. For comparison, a typical ringfort in Ireland, the most common early medieval field monument, tends to run between 20 and 60 metres in diameter. Something this large might have served a more significant or specialised function, though without excavation the date and purpose remain open questions.