What remains is not a wall or even a clear earthwork, but a scatter of bare, stony patches spread across the soil. Walk the ground carefully, though, and those patches resolve into a circle, the ghost of an enclosure that was once a working farmstead, probably in use during the early medieval period, roughly between the fifth and twelfth centuries.

A rath, as this type of monument is commonly known in Ireland, was a circular enclosure defined by an earthen bank and an outer ditch, or fosse, used as a defended farmstead or the residence of a local lord. The Rockspring example had a reasonably long cartographic life before it finally succumbed. On the Ordnance Survey six-inch map of 1842, the arc of the enclosure, running from south-south-east to north-west, was still visible and had been absorbed into the local field boundary system, its curve doing quiet duty as a fence line. By the time the 1905 and 1937 editions of the same map were produced, those field fences had been removed, and the surviving arc, approximately 35 metres across, was recorded as a hachured bank, the conventional cartographic symbol for an earthwork. At some point after that, the bank was levelled entirely. The story of the site is, in a sense, the story told by successive maps: gradual erasure, each generation removing a little more of what the last had left.

The most revealing evidence now comes not from ground level but from the air. An aerial photograph captured the site as a cropmark, the buried fosse showing up as a difference in crop growth above the disturbed soil of the old ditch. This is a common way such sites are rediscovered; crops growing over a filled ditch tend to stay greener longer, or ripen at a different rate, than those in the surrounding field, tracing the original shape with surprising precision even where nothing is visible to a person standing in the field itself.