That label, repeated across two separate surveys eighty years apart, almost certainly points to a souterrain, an underground stone-lined passage or chamber that early medieval Irish farming communities built beneath their settlements for storage or refuge. Yet when surveyors examined the site in detail, no trace of any such feature remained visible on the ground. Whatever the cave once was, it has either collapsed, silted over entirely, or been quietly swallowed by the pasture that now covers the interior.

The earthwork itself is a rath, the Irish term for a ringfort, a roughly circular enclosure defined by a bank and ditch that served as a farmstead during the early medieval period, broadly from around the fifth to the twelfth century. Thousands survive across Ireland in varying states of preservation. The Ballycasey example was recorded on the 1841 six-inch Ordnance Survey map as a roughly circular embanked enclosure with a diameter of approximately forty metres, a modest but typical size. By the time Denis Power compiled the site record, uploaded in August 2011, the northern and western sides had been truncated by field boundaries, leaving only the eastern to south-south-eastern arc intact as a scarped edge, roughly 0.8 metres high and 10 metres wide, enclosing a wedge-shaped area measuring around 32 metres north to south and 34 metres east to west. The interior slopes gently downward toward the north and is given over entirely to grazing.

The site sits atop a hill in the north-west corner of a large field, with a public road running immediately to its west, which makes it relatively straightforward to locate from the roadside. The surviving bank section is most clearly read from the east, where the scarped edge gives a cleaner sense of the original enclosure line. The interior offers little to see beyond the gentle gradient of the pasture, though knowing that two generations of cartographers marked a cave here lends the grass a certain weight. Visiting in winter or early spring, when vegetation is low, gives the best chance of reading the earthwork's profile against the hillside.