This is a rath, the Irish term for a ringfort, a type of enclosed farmstead built and occupied across Ireland roughly between the early medieval period and the twelfth century. Thousands of them survive across the country in varying states of preservation, but this one at Barleyhill has an unusual quality: the bank that once defined it has been partly co-opted by the bank of the wood itself, so the rath and the landscape around it have grown into each other over the centuries.

The enclosure is oval in plan, measuring 34.5 metres north to south and 24 metres east to west, and it slopes noticeably, dropping only about 0.2 metres toward the west but falling a more substantial 1.9 metres on the eastern side. The earthen bank that defines it has a base width of five to six metres and stands between 1.1 and 1.3 metres high on the exterior. On the north-west to north-east arc, this bank merges with the bank of the surrounding wood, making the two structures effectively one. Beyond the bank, a fosse, which is a defensive ditch dug around the outside of the enclosure, survives best on the south-east to south-west side; it is around 6.2 metres wide at the top and 0.8 metres deep. At the north-east there is a gap of roughly 3.3 metres in the bank, which may mark the original entrance to the enclosure, though it is also possible this is simply a point where the bank has been damaged or eroded over time. The interior is grass-covered now, shaded by mature trees and punctuated by old stumps, the whole thing occupying what was once the north-facing spine of a ridge running roughly north-north-west to south-south-east.