Where local tradition speaks of a cave, the first edition of the Ordnance Survey 6-inch map shows nothing but good agricultural land. This souterrain, as such underground structures are properly known in archaeological terms, represents one of many hidden features of the Irish landscape that have slipped through the cracks of official documentation.

Souterrains are artificial underground passages that were commonly built in Ireland during the early medieval period, typically between the 6th and 12th centuries. These subterranean chambers served various purposes; some were used for storage, keeping food cool and dry, whilst others may have provided temporary refuge during raids. The Magherasollus example, though unmarked on early maps, would have been part of this broader tradition of underground construction that characterises rural Irish settlements from this era.

The site’s documentation comes from the comprehensive Archaeological Survey of County Donegal, compiled in 1983 by Brian Lacey and his team of researchers. This survey attempted to catalogue the county’s archaeological heritage from the Mesolithic period through to the 17th century, capturing sites like this souterrain that might otherwise be forgotten. The fact that it existed in what was described as “good land” suggests it was likely associated with a prosperous farmstead, though any above-ground structures have long since vanished, leaving only the underground passage as testament to the lives once lived here.