On the 1930 edition of the Ordnance Survey six-inch map, the spot is marked with hachures, the short radiating lines cartographers use to suggest a hollow or earthwork of some kind, implying something worth noting. When the site was examined in person in 1984, that intriguing symbol resolved itself into something altogether more modest: a disused sand pit, long since abandoned.

Eskers are the long, winding ridges of sand and gravel left behind by meltwater streams that once flowed beneath glaciers during the last ice age. Ireland has a remarkable number of them, running like raised causeways across the midland plain, and they were valued for centuries as natural routeways across boggy ground. The gravelly material they contain also made them targets for small-scale extraction, and sand pits like the one at Knockanarra were practical, local operations, dug by hand to supply building or agricultural needs. The gap between the 1930 mapping and the 1984 inspection is a reminder of how long a mark on a map can outlast the activity that created it, and how a cartographic symbol can carry more mystery than the ground beneath it.