Depending on which map or record you consult, it is either an ancient enclosure of archaeological significance or a set of disused gravel pits, and the difference between those two things is considerable.

The confusion has a paper trail. An Ordnance Survey map from 1939 shows a circular feature marked with hachures, the small lines cartographers use to indicate a depression or earthwork. That circular shape was enough to earn the site a listing as a possible enclosure in both the Sites and Monuments Record of 1992 and the Record of Monuments and Places of 1996. An enclosure, in this context, typically refers to a roughly circular area bounded by a bank or ditch, often associated with early medieval settlement or farming activity in Ireland. The complication is that the older OS 25-inch map names the very same feature as gravel pits, disused. A circular pit left by extraction work and a circular earthwork raised by human habitation can look remarkably similar from above, and the Doonass site has never been firmly resolved into one or the other.