A rath, as these early medieval earthwork enclosures are commonly known, would once have consisted of a circular bank of earth enclosing a farmstead or settlement, often with a fosse, or ditch, dug around the outside. The one at Ballygullen had the bank but no fosse, and by 1987 even the bank itself had ceased to be visible at ground level. What remains is a kind of memory in the earth: local knowledge holds that when the field is ploughed, a patch of dark soil appears, tracing the outline of what once lay there.

The site has been tracked across more than a century of cartographic and field records. The 1839 edition of the Ordnance Survey six-inch map recorded it as a circular enclosure planted with trees, roughly fifty metres in diameter, which suggests it was a recognisable feature in the landscape at that point, perhaps even deliberately preserved. By the time the same area was mapped again in the 1940 edition, it appeared only as a hachured feature, a cartographic convention indicating a raised earthwork, still with an external diameter of around fifty metres. A field record from 1940 gives more precise internal measurements: approximately 33.5 metres north to south and 31 metres east to west, with an earthen bank between 3.5 and 4.5 metres wide and standing between one and one and a half metres high. The site sits on a slight west-facing slope, which would have been a typical and practical choice for a rath, offering modest drainage and outlook. Sometime in the decades between that 1940 survey and 1987, the bank was levelled entirely, most likely by agricultural activity.

What makes this particular site quietly interesting is the gap between its cartographic presence and its physical absence. It appears on two editions of the OS maps, was measured in detail in 1940, and yet left so little behind that a generation later it could only be located, if at all, by the discolouration of ploughed soil. That dark patch, where disturbed organic material or the compressed fill of an ancient bank sits differently in the earth, is a common way that levelled monuments continue to betray themselves to anyone paying attention.