They cannot be seen by walking the field, and no earthwork rises above the grass to hint at what lies below. They appear only from above, as cropmarks, the subtle discolouration in vegetation that sometimes betrays buried features to a camera or a satellite sensor. In this case, the two possible ring-ditches at Mannin measure somewhere between eight and ten metres in diameter and sit roughly thirty-three metres apart, close enough to suggest a relationship between them, though what that relationship was remains an open question.

A ring-ditch is generally understood to be the circular trench that once surrounded a burial mound or a ritual enclosure. Over centuries, the mound material can be ploughed or eroded away entirely, leaving only the ditch cut into the subsoil below. That buried ditch, filled with slightly different soil than the surrounding ground, can encourage or inhibit plant growth in ways that become visible from the air, particularly during dry summers when stressed vegetation picks out the contrast most sharply. These two cropmarks at Mannin were not identified through ground survey but through satellite imagery, spotted and reported by Jean-Charles Caillère. The find is a small example of how much of the Irish archaeological landscape remains unverified, neither excavated nor dismissed, simply waiting.