The ground lifts slightly, levels into a hollow terrace, then drops away in a low but distinct scarp, the whole circuit measuring roughly thirty metres north to south and twenty-seven metres east to west. It is easy to walk past without registering what you are looking at, which is part of what makes the site quietly compelling.

A ringfort, or rath, is an enclosed farmstead typically dating from the early medieval period, roughly 500 to 1200 AD, consisting of a roughly circular earthen bank, sometimes accompanied by a fosse, the drainage ditch dug immediately outside the bank. At Castleterry, the fosse survives as a shallow depression running from the north-west around to the south-south-east, where a stone field boundary has been built along its outer edge, effectively borrowing the ancient earthwork as a ready-made boundary line. That detail, a farmer centuries later finding the old ditch still useful enough to wall along, is visible on Ordnance Survey six-inch maps from 1842, 1905, and 1935, each of which records the enclosure as a hachured circle of around fifty metres in diameter. By 1905 and again in 1935, a solid field boundary line is shown running over the hachures themselves, confirming that the ringfort's perimeter had been absorbed into the working agricultural landscape while its form remained legible beneath. The one-metre scarp that defines the raised interior is unspectacular by any dramatic measure, but it has endured in open pasture for well over a millennium, slowly settling into the hillside rather than disappearing entirely.