Easy to walk past, easy to misread as a natural depression, it is in fact a bullaun stone, a type of ancient carved feature found at sacred and ceremonial sites across Ireland. The word bullaun comes from the Irish word for bowl, and these hollowed stones are thought to have served ritual purposes, possibly connected with water, healing, or devotion, though their exact origins and functions remain subjects of debate among archaeologists.

The slab itself is modest in size, roughly 1.9 metres from east to west and about 0.7 metres wide, and the carved bowl sits close to the eastern edge, measuring around 22 centimetres across and about 10 centimetres deep. What makes its location particularly interesting is its relationship to the mass rock just uphill. Mass rocks are flat stones or natural outcrops used as improvised altars during the Penal period in Ireland, roughly the late seventeenth and eighteenth centuries, when Catholic worship was suppressed and priests conducted services outdoors in remote places. The proximity of the bullaun to such a site suggests that this corner of Derrynakilla carried a layered significance, with the older carved stone and the later place of clandestine worship occupying the same sloped ground.