The image, taken as part of survey St. Joseph ATC 9, shows a substantial circular cropmark measuring between 40 and 50 metres across. These marks, visible only from above, occur when buried archaeological features affect the growth of crops above them, creating tell-tale patterns that hint at ancient structures hidden underground.

The site sits in what's described as excellent farmland, which perhaps explains why it hasn't been excavated or examined on foot. Many such discoveries across Ireland remain uninvestigated, their secrets preserved beneath layers of soil and centuries of agricultural activity. The circular shape and considerable size suggest this could be anything from a prehistoric enclosure to a ringfort, both common features in the Irish landscape that served various purposes from defensive settlements to ceremonial sites.

This particular finding comes from the Archaeological Survey of County Donegal, a comprehensive catalogue compiled in 1983 that documents the county's archaeological heritage spanning from the Mesolithic period right through to the 17th century. The survey, undertaken by a team of archaeologists including Brian Lacey and several colleagues, represents one of the most thorough archaeological inventories of any Irish county, though many of its entries, like this one at Cottown, remain tantalisingly unexplored.