This ancient cashel, a type of stone fort common in early medieval Ireland, consists of a circular enclosure surrounded by a partially ruined stone wall that once stood an impressive 2.45 metres wide. What makes this site particularly intriguing is the evidence of a second, outer wall; between five and eight metres beyond the inner fortification, carefully placed single stones suggest this additional defensive ring would have cleverly incorporated natural rock outcrops into its design.

The interior of the cashel reveals a complex history of occupation and use. The ground within is notably uneven, with a concentration of stones towards the southeast that likely marks the remains of an internal structure, perhaps a dwelling or storage building. Most remarkably, the northwest section contains a partially filled souterrain; a type of underground passage that was common in Ireland during the early medieval period. This subterranean feature can be traced for nine metres along the inner face of the cashel wall before making a sharp right-angled turn and extending another three metres towards the centre of the enclosure.

The souterrain itself showcases the skilled drystone construction techniques of its builders, with walls carefully fitted without mortar. Where it remains measurable, the passage is approximately half a metre wide and 0.6 metres deep below its roof lintels, which sit flush with the ground level of the cashel's interior. This hidden architectural feature would have served multiple purposes for the site's inhabitants, potentially functioning as cold storage for food, a place of refuge during raids, or a secure location for storing valuable goods. The entire complex at Glentidaly offers a tangible connection to Ireland's early medieval past, when such fortified homesteads dotted the landscape, serving as centres of agricultural production and local power.