This is a cashel, a type of ringfort built from drystone rather than earthen banks, and its near-perfect circular form, measuring just over thirty-one metres across, still reads clearly from the ground despite centuries of slow deterioration.

Cashels were typically built during the early medieval period, roughly between the fifth and twelfth centuries, and served as enclosed farmsteads for free farming families. The drystone walls, constructed without mortar, were built to define territory, protect livestock, and signal status as much as to defend against attack. At Ardamullivan, that wall has largely fallen in on itself, leaving a grassed-over ring of rubble rather than upstanding masonry, but the coherence of the enclosure remains. The site is described as being in fair condition, which in this context means the essential shape survives even if the structure no longer stands proud.