The land at Hundred Acres shows nothing unusual to the eye today, no hollow, no opening, no depression that might hint at what lies beneath or once lay there. The only confident record of this feature is cartographic: the Ordnance Survey's six-inch map of 1838, which marks the word "Cave" on the south-south-western edge of what was then a ringfort. That ringfort, a circular enclosure of the kind built across Ireland from the early medieval period onwards, has since been levelled, and whatever the cave was, or whether it survives in any form underground, is no longer knowable from the surface.

The 1838 OS mapping was the product of a remarkable national survey, the first large-scale systematic mapping of Ireland, and its surveyors recorded features, place-names, and landscape details with considerable care. That they noted a cave at this location suggests something was visible or at least locally known at the time. Caves and souterrains, the latter being man-made underground stone-lined passages sometimes associated with ringforts and used for storage or refuge, were occasionally conflated by early recorders, and it is possible the "Cave" label here refers to an artificial rather than a natural feature. Without excavation, the distinction cannot be made. What is clear is that by the time the site was formally examined in more recent decades, the ringfort itself had been erased by agricultural activity, taking whatever surface evidence remained with it.