It is a souterrain, a type of structure built during the early medieval period in Ireland, typically consisting of one or more dry-stone chambers or tunnels dug into the earth or constructed below ground level. Their precise purposes remain debated among archaeologists, though uses ranging from cold storage to refuge during raids are most commonly proposed. What is certain is that they required considerable communal effort to construct, and their presence in a townland usually points to settled, organised habitation nearby.

Carrowleagh, like many townlands across Mayo, sits within a landscape that has been continuously worked and inhabited for millennia. The county is dense with early medieval and prehistoric activity, and souterrains are found scattered across it in varying states of preservation and documentation. Some survive as accessible chambers; others have partially collapsed or been built over. Without more detailed records currently available for this particular example, its dimensions, condition, and relationship to any surrounding settlement remain unclear. What can be said is that it has been formally identified and recorded as an archaeological monument, placing it within a broader county-wide pattern of underground construction that speaks to the ingenuity and anxiety of early medieval rural life.