It exists, for now, only as a ghost in the grass, a cropmark betrayed by differential growth in a dry summer and caught by an aerial camera in July 1989. What the photograph revealed was the outline of a fosse, the ditch that once defined a large roughly trapezium-shaped enclosure, running approximately 60 metres east to west and 70 metres north to south. The shape alone sets it apart; most Irish enclosures tend toward the circular or oval, so a trapezoidal plan is an unusual detail worth pausing over.

Cropmarks form when buried features such as ditches or foundations affect the soil's moisture and nutrient content, causing crops or grass above them to grow at slightly different rates, differences invisible at ground level but legible from the air, particularly in dry conditions. The enclosure at Corbally was identified through this method as part of the Cork Aerial Survey and Archaeological Project, which captured the image in 1989. The fosse outline suggests the site once had a substantial boundary ditch, and the entrance, positioned off-centre to the north on the eastern side, is the kind of specific asymmetry that tends to reflect deliberate design rather than later alteration. Without excavation it is difficult to assign a firm date or function, though large enclosed sites of this general character in Ireland range from the prehistoric into the early medieval period.