Most examples of this early medieval settlement form, built across Ireland roughly between the fifth and twelfth centuries, have at least one obvious gap in their enclosing banks where people and livestock once passed through. The rath at Crone Beg offers no such clue. Whatever threshold once existed here, the ground has long since smoothed it away, leaving a nearly complete circuit of earthworks and no obvious way in.

The site is a bivallate ringfort, meaning it has two concentric earthen banks rather than the single bank more commonly encountered. The inner bank, running from south around west to north, measures about four metres wide and stands nearly a metre high. Outside it sits a fosse, a defensive ditch roughly three to four metres wide and a metre deep, and beyond that a second, slightly taller outer bank. The whole enclosure spans thirty-eight metres in diameter. What gives the place a slightly disorienting quality is the way the eastern interior sits 1.8 metres above the surrounding ground level outside the earthworks, the result of the natural slope on which the fort was laid out, a gentle south-southeast-facing incline. Standing inside, the ground beneath your feet is considerably higher on one side than the world beyond the banks on the other. No internal features have been identified, so whatever structures once occupied the interior, a farmstead or a family's compound, have left nothing visible at ground level.