This is a ring barrow, a type of funerary enclosure typically associated with the Bronze Age, and what sets this one apart at first glance is its form: not a circle but a D-shape, a flattened platform roughly 18.7 metres north to south and 15 metres east to west, ringed by a shallow ditch known as a fosse and a low outer bank.

The dimensions are modest but legible on the ground. The fosse is about a metre wide, and the enclosing bank rises only 0.4 metres on its outer face and 0.2 metres on the inner, the kind of subtle earthwork that rewards a patient eye rather than announcing itself from a distance. Ring barrows of this type served as ceremonial or burial enclosures, the fosse and bank demarcating a bounded space around a central platform where the dead, or rites associated with the dead, were accommodated. The Coolnacrutta example has not escaped the pressures of the centuries intact: the south-western portion of the monument was damaged by cultivation ridges, the long parallel earthen beds characteristic of nineteenth-century lazy-bed potato farming, a reminder that the land was worked hard during a period of acute agricultural necessity.