Where the more familiar earthwork ringforts of Ireland were raised from ditches and ramparts of compacted soil and turf, a cashel uses whatever stone the local landscape provides in abundance, and along this stretch of the north Mayo coast, stone is rarely in short supply. These circular enclosures were typically built during the early medieval period, roughly between the fifth and twelfth centuries, and served as farmsteads and places of security for a family and their livestock rather than as military fortifications in any formal sense.

Doonfeeny itself sits in a part of Mayo with a long and layered past. The area lies not far from Downpatrick Head, a place of early Christian association, and the broader landscape of north Mayo contains some of the most significant prehistoric and early medieval remains in the country, from the Céide Fields to the north, with their Neolithic field systems preserved beneath the bog, to scattered ringforts and ecclesiastical sites along the coast. A cashel in this setting is not unusual in the abstract, but each surviving example represents a particular community's decision about where to live and how to enclose that life in stone, decisions made well over a thousand years ago and still faintly legible in the outline of a wall.