That is not unusual for ancient earthworks, which are steadily worn down by agriculture and weather, but it does create a particular kind of historical puzzle: a place that exists more convincingly on paper than it does in the field.

The earliest clear record of the site comes from the 1842 OS six-inch map, where it appears as a rectangular field, roughly 30 metres north to south and 25 metres east to west. By the 1904 edition, cartographers had rendered it with hachuring, the small lines surveyors used to indicate an earthwork or raised boundary, suggesting the banks were still visible at that point, or at least still remembered. The 1938 map reverts to showing it simply as a field boundary. Whatever remained of the earthen walls had by then either collapsed entirely or been absorbed into the working landscape of the farm. What the maps cannot settle is when the enclosure was originally built or by whom. Rectangular enclosures of this kind in Ireland are associated with a broad sweep of periods, from early medieval farming settlements through to later medieval land divisions. More intriguing is the record of a possible souterrain within its interior. A souterrain is an underground stone-lined passage or chamber, typically associated with early medieval ringforts and used for storage or refuge, and their presence beneath a site is often the most durable trace of early occupation, long after any surface features have been ploughed or grazed away.

There is nothing to see at Rathduff in any conventional sense. The enclosure survives only in the cartographic record and in whatever may lie underground, unexcavated. That combination, a blank field carrying a long paper trail and a possible hidden chamber beneath, is itself a reasonable summary of how much early Irish settlement remains, known about but not yet understood.