It is neither. When someone finally went to look properly in 1999, what they found was a roughly twenty-two metre by twenty-one metre hollow in the earth, almost certainly a feature of the designed grounds of Port House rather than anything prehistoric or defensive.

The confusion is understandable. Ireland's Record of Monuments and Places, which logs sites of potential archaeological significance across the country, had it down as an enclosure, a broad category that can cover everything from Iron Age ring-forts to medieval farmsteads. George Coffey's 1987 note went further and called it a fort outright. But its position, situated between Port House itself and the gateway to a disused kitchen garden, places it squarely within the logic of an ornamental or working estate landscape. Sunken gardens and recessed ground-level features were common enough in designed landscapes of the eighteenth and nineteenth centuries, sometimes used for kitchen garden beds, sometimes as more purely aesthetic elements. Without closer investigation it is impossible to say exactly when this one was made or what its precise function was, but its rectangular geometry and its relationship to the house and garden structures around it point firmly away from antiquity.