This subcircular stone mound measures approximately 4.6 metres across and rises just over a metre in height. Whilst cairns of this type are common throughout Ireland, this particular example at Dún Ailt holds something rather special; an inscribed cross slab that crowns its summit.

The undressed stone slab measures roughly 1.14 metres in length and varies between 22 to 34 centimetres in width. What makes it particularly noteworthy are the crosses carefully incised into three of its faces. The western face displays a bar cross with distinctive terminals; a pear shaped ending at the bottom and a rectangular terminal with internal markings at the top. The northern side bears a simple Latin cross topped with a bar terminal, whilst the eastern face shows another Latin cross, this time with bar terminals on each arm. These markings, though thinly carved and weathered by centuries of exposure to the Atlantic elements, represent an important example of early Christian stone carving in the region.

The site forms part of County Donegal's rich archaeological landscape, documented in the comprehensive Archaeological Survey compiled by Brian Lacey and his team in 1983. The combination of the cairn and cross slab suggests this location held significance for the local community, possibly serving as a territorial marker, burial site, or place of religious importance. The crosses themselves likely date from the early medieval period, when such simple incised designs were common throughout the Irish countryside, marking the spread of Christianity across the island.