A cashel is a ringfort built from stone rather than earth and timber, its thick circular wall enclosing a farmstead or settlement that would have housed an early medieval family and their animals. Where earthen ringforts rely on banked ditches, a cashel relies on the weight and permanence of dry-stone construction, which is perhaps why so many have outlasted the people who raised them.

Ringforts of both types were built predominantly during the early medieval period in Ireland, roughly between the fifth and twelfth centuries, and they are among the most numerous archaeological monument types in the country. Glenbaun lies in a part of Mayo shaped by Atlantic exposure, thin soils, and a long history of subsistence farming, and a stone enclosure here would have made practical sense: timber was scarce, but stone was not. The cashel form suited the terrain and the available materials. Beyond its classification and location, the specific history of this particular enclosure, who built it, when exactly, and what became of the settlement it once protected, remains unrecorded in publicly available sources.