A rath, to use the Irish term, is a roughly circular enclosure defined by one or more earthen banks and a fosse, the ditch dug to provide the material for those banks. They were the farmsteads of early medieval Ireland, typically dating from somewhere between the fifth and twelfth centuries, and several tens of thousands of them are thought to have existed across the island. This one, measuring roughly 47 metres north to south and 45 metres east to west, belongs to the more substantial end of the type: it had two banks with a fosse between them, a doubled line of defence that would have made the enclosed space considerably more imposing in its working life than anything visible today suggests.

What survives is partial and uneven. The inner bank can still be traced from the south-east around to the south-south-west, but north of that point the ground drops away in a scarp rather than presenting any formed earthwork, and from the south-south-west around to the north there is no visible surface trace at all. The outer bank and its accompanying fosse fare little better, surviving only along a short arc from the south to the west-south-west. A trackway, presumably of later origin, has cut through the line of the fosse and outer bank somewhere between the north-east and south-east, which accounts for at least some of the damage to the circuit. The name Sheeaun Hill is itself suggestive: the Irish word "sídhán" refers to a small fairy mound or earthen mound associated with the otherworld, and it is a name that in many parts of Ireland attaches itself to ancient earthworks that were never fully understood by later generations but were treated with a certain cautious respect regardless.