At Caherulla in County Kerry, there was once a rath, the Irish term for a ringfort, which is a circular earthen enclosure typically dating from the early medieval period and used as a defended farmstead. It was recorded on the Ordnance Survey map of 1842, carefully noted as a circular enclosure in the landscape. By the time the revised edition was produced in 1916, it had disappeared from the map entirely, and today no surface trace of it remains whatsoever.

The gap between those two surveys, a period of roughly seventy years, is when this particular piece of the past was erased. Whether through agricultural clearance, land improvement schemes, or simple neglect of an earthwork that had already lost its meaning to those working the surrounding land, the rath at Caherulla crossed from physical feature to cartographic memory to nothing at all. Its existence is now known only because the 1842 surveyors thought it worth marking down, a circular form on the ground that someone, at least once, considered significant enough to record. C. Toal's North Kerry Archaeological Survey, published in 1995, preserves the reference, which is itself the only reason the site can be identified at all.