On the ground it presents as a low, undulating oval raised slightly above the surrounding grassland, ringed by a fosse and a broad outer bank, with a causeway extending westward to a circular raised platform. For decades it was catalogued alongside the ancient earthworks of the Irish countryside. Then an estate map dated 1749 provided a different explanation entirely: what generations of aerial surveyors had been photographing was, in all likelihood, the ghost of a formal garden.

Kilcooly Abbey, a Cistercian foundation, had been converted into a residence sometime in the late seventeenth or early eighteenth century, and the household that occupied it appears to have laid out an elaborate oval garden with projections extending from both its eastern and western sides. The 1749 map records this layout clearly, matching the oval earthwork and its surviving western causeway and circular terminus. When the present Kilcooly House was built around 1760 and a ha-ha was constructed to the east of the old garden enclosure, a ha-ha being a sunken boundary ditch designed to keep livestock out of formal grounds without interrupting the view, the eastern projection was levelled in the process. What remains under the grass today is the western half of that arrangement, preserved well enough that its dimensions can still be measured: the outer bank spans nearly twelve metres at its base, and the fosse surrounding the oval reaches eight metres across. The garden outlasted its owners, its flowers, and even its identity, surviving into the present as an earthwork that fooled the eye of more than one trained archaeologist.