It survives only as a cartographic ghost, a shape that appeared on an Ordnance Survey map and then, effectively, vanished.

The enclosure does not appear on the 1837 edition of the OS 6-inch map, the great nineteenth-century survey that recorded Ireland's landscape in meticulous detail. By the 1912 edition, however, it had been captured as a hachured outline, roughly pentagonal in shape, measuring approximately 30 metres across both its northeast-southwest and northwest-southeast axes. Hachuring on such maps typically indicated a raised or earthen feature, the kind of low bank or mounded perimeter that might once have defined a farmstead, a field boundary, or a small enclosed settlement. At some point between that 1912 survey and the present, whatever earthwork had been there was levelled entirely. The ground gives nothing away now.

What makes the site quietly absorbing is precisely that gap between the two maps. In 1837, nothing worth recording. By 1912, a defined pentagonal monument, roughly the scale of a large house plot. And now, nothing again. Whether it was ploughed out, drained into submission by agricultural improvement on that wet, low-lying ground, or simply collapsed over time, the record does not say. The enclosure at Willowbrook is, in the most literal sense, a place that exists only on paper.