This stone ringfort, measuring roughly 18 metres across, consists of a circular defensive wall built from local stone and turf. Though time and weather have taken their toll, particularly on the southwest section where the wall has partially collapsed, the structure still commands an impressive presence on its elevated position.

The cashel’s builders chose their location wisely; the natural rock outcrop provided both a solid foundation and strategic advantage. Anyone approaching would have been visible long before reaching the fortified enclosure, whilst those inside enjoyed sweeping views across the surrounding countryside. Just below the fort lies an unexpected feature: a broad stretch of elevated meadow so smooth and well preserved it resembles a maintained lawn, perhaps once used for grazing livestock safely within sight of the settlement.

These ringforts, known locally as cashels when built primarily of stone, were typical dwelling places for prosperous farming families during the early medieval period, roughly from the 5th to 12th centuries. The Kilmonaster Middle cashel follows the standard design of these settlements, with its circular wall creating a protected space where wooden or stone buildings would have stood. Archaeological surveys suggest hundreds of similar sites dot the Donegal landscape, each one a testament to the dispersed rural communities that once thrived across Ireland before the arrival of the Normans changed settlement patterns forever.