In satellite imagery, a near-perfect circle, roughly 42 metres across, appears as a cropmark in the tillage, the outline of a ditch that has not been visible at ground level for a very long time, if it ever was in living memory.

Cropmarks form when buried features, ditches, walls, or pits, affect the growth of whatever is planted above them. A filled-in ditch retains more moisture than the compacted ground around it, so the crop above it grows taller or greener, and from altitude the buried geometry becomes legible. The circular enclosure at Knocknanuss fits a pattern found across Ireland, where enclosed settlements or ritual sites defined by a circular ditch were constructed throughout prehistory and into the early medieval period. This particular example came to wider attention through Apple Maps imagery, identified by Jean-Charles Caillère and recorded in 2022. Its diameter of approximately 42 metres places it within the range typical of a rath or ringfort, though without excavation the precise date and function of the enclosure cannot be determined.

Knocknanuss itself carries its own layer of history. It was the site of a significant Confederate and Royalist defeat in 1647, when Parliamentary forces under Murrough O'Brien routed an army under Alasdair MacColla. That battle left its mark on the place name in local memory, which makes the quiet reappearance of something far older in the same townland a gentle reminder that the ground holds more than any single century.