The example at Knockbrack in County Kilkenny is a rath, the commonest type of ringfort, formed by one or more circular earthen banks and ditches enclosing a domestic space. In early medieval Ireland, roughly the fifth to the twelfth centuries, these enclosures served as the farmsteads of free farmers and minor lords, the bank and ditch marking territory as much as providing defence. That so many survive at all is partly because later generations considered them the homes of the fairy folk and left them alone.

Knockbrack itself, whose name derives from the Irish "cnoc breac", meaning speckled or dappled hill, sits in the quiet agricultural interior of Kilkenny, a county where the density of such earthworks reflects centuries of early Irish settlement. The rath would originally have enclosed timber or wattle buildings, perhaps a house, outbuildings, and a souterrain, an underground stone-lined passage used for storage or refuge. Over the centuries, ploughing and land improvement have erased countless examples, making any survivor worth pausing over, even one whose individual history remains, for now, undocumented.