The site exists, for now, primarily as a cropmark, the kind of subtle discolouration in growing or ripening crops that betrays buried features beneath the soil. Where a fosse, a defensive or boundary ditch, was once cut into the ground, the disturbed earth affects moisture retention and root depth in ways that show up in the crop above, often only legible from altitude and only during certain growing conditions.

The enclosure at Kilmagar was identified and reported by Jean-Charles Caillère, who noticed it on satellite imagery available through Apple Maps. The site sits in tillage ground, which is both the reason it survives unrecognised at ground level and the condition that periodically makes it visible from the air. The main feature is a single fosse defining the circular form, and there is also a suggestion of a second, outer fosse in the north-east quadrant, which would be consistent with more elaborately defended or formally bounded enclosures found elsewhere in the Irish landscape. Circular enclosures of this type are often associated with the early medieval period, though without excavation the date and function of this one remain open questions.