Near the old ecclesiastical settlement of Kilcullen in County Kildare, there once existed an enclosure that has since vanished so completely that it left not so much as a crop mark or a grassy ring to hint at its former presence. What makes it notable now is almost entirely the fact of its disappearance, and the single early-nineteenth-century map on which it was captured before that disappearance was complete.

In 1815, a surveyor named Longfield mapped the Glebe of Kilcullen, the landholding attached to the local Church of Ireland parish, and on that map he recorded the enclosure using two concentric circles, the conventional shorthand for a roughly circular earthwork. The map, preserved in the National Library of Ireland, is the only known document to show it. When the Ordnance Survey later produced their meticulous series of Irish maps across the nineteenth century, beginning in the 1830s, no trace of the feature appeared on any edition. By 1986, when the site was assessed on the ground, nothing whatsoever was visible at the surface. An enclosure of this kind, typically a bank and ditch arrangement marking out a defined area, might have been prehistoric, early medieval, or associated with the ecclesiastical history of Oldkilcullen itself, which was an important early Christian site. Without further evidence, none of those possibilities can be confirmed or ruled out.

What remains is essentially a cartographic ghost: a feature that existed clearly enough in 1815 to be worth recording, and that had already been erased, whether by ploughing, land improvement, or simple time, before anyone thought to look for it again.