At Lissaleen in County Galway, an enclosure of roughly twenty metres across was detected not by anyone walking the land but by a reconnaissance flight in July 1965. The camera caught what the eye on the ground could not: a faint semicircular outline defined by a subtle difference in vegetation growth, the kind of mark that suggests buried or disturbed soil beneath. No surface trace survives today, and a modern field boundary cutting across the south-eastern side has further broken what was already a fragmentary shape.

The 1965 flight, recorded under the Cambridge University Committee for Aerial Photography reference ALR 82, captured the site at a moment when differential crop or grass growth made the buried feature legible from altitude. Such vegetation marks appear when buried ditches or banks alter the moisture and nutrient content of the soil above them, causing plants to grow slightly taller or greener along those lines. The enclosure sits roughly one hundred metres north-east of a separate, catalogued enclosure nearby, suggesting this part of north Galway may have seen more organised settlement or agricultural activity than the current empty fields imply. A natural hollow lies immediately to the south of the site, which may or may not be connected to however the enclosure was originally used. Without excavation, the date and function of the feature remain open questions.