What was long recorded on Ordnance Survey maps as a single enclosure turns out, on closer inspection, to be a substantially more complex arrangement of collapsed ramparts, a causeway-like structure, and subsidiary enclosures spread across a narrow ridge running roughly two hundred metres from east to west. The spur commands sightlines in every direction, taking in the main passes through the Stacks Mountains to the north-east and the Slieve Mish range to the south-west, as well as two fording points on the River Lee below. Early edition maps record the surrounding low ground as marshy, which would have left the spur looking very much like a promontory, approachable on dry land only from the east.

A survey carried out by Michael Connolly in 1996 and 1997 as part of a wider examination of the Lee Valley revealed that the site had been significantly underestimated. The northern side of the spur is defended by two concentric collapsed ramparts of stone and earth, the inner one still readable at ground level, the outer visible only in good light. The southern side has a single rampart. Along the western half of the spur these earthworks are reasonably continuous, but they become fragmentary toward the eastern end, where later structures appear to have been built directly onto or into the rampart line, partly obscuring it. The ramparts were constructed partly by scarping back into the natural slope of the bedrock and partly by raising conventional earthen banks; the enclosed area measures roughly 88 metres north to south and 200 metres east to west, giving a total of approximately 1.76 hectares. The limestone bedrock itself, carboniferous in origin and barely covered by soil, preserves a notable concentration of fossil material across the surface of the spur. At the eastern end, the most structurally intricate part of the site, a 23-metre embanked channel runs east to west from the level ground up to the wall of the centrally placed enclosure. Whether this feature functioned as a formal entrance passage or served some other purpose has not been conclusively established. Immediately adjoining it are a shallow sub-circular depression and a small horseshoe-shaped enclosure, both of which show clearly on aerial photography but are considerably harder to make out at ground level.