A 1961 aerial photograph captured at least one distinct circular cropmark measuring between 30 and 40 metres in diameter; a ghostly outline visible only from above where differences in crop growth betray the presence of buried archaeological features. The photograph hints at additional possible structures nearby, though these remain more ambiguous in their interpretation.

These cropmarks represent a type of archaeological evidence that often goes unnoticed at ground level. When ancient ditches, pits, or foundation trenches are filled in over time, they retain more moisture than the surrounding soil, causing crops above them to grow differently; sometimes taller and greener, sometimes shorter and stressed, depending on weather conditions. In this case, the circular mark likely indicates the remains of an enclosed settlement or ceremonial site, possibly dating anywhere from the Bronze Age through to the medieval period, though without excavation it's impossible to be certain.

The site sits in what's described as good farmland, which explains both its potential ancient appeal and why it hasn't been physically investigated. The information comes from the comprehensive Archaeological Survey of County Donegal, compiled in 1983 by a team of archaeologists led by Brian Lacey. This survey catalogued field antiquities spanning from the Mesolithic period right through to the 17th century, creating an invaluable record of Donegal's rich archaeological heritage, much of which, like these cropmarks at Clashygowan, remains hidden just beneath the surface of the everyday landscape.