It measures roughly two and a half metres long and a metre high, its natural surface doing the work that carved stone or timber would have done in a church. A metal cross and a plaque, lettered in Irish, now mark the spot, recording that Mass was said here during the Penal Laws, the series of statutes enacted from the late seventeenth century onward that sought to suppress Catholic worship and strip Catholic clergy of any legal standing in Ireland.

Mass-rocks are one of the more quietly charged features of the Irish landscape. When celebrating Mass was effectively outlawed and priests faced transportation or execution, congregations moved outdoors, gathering in remote or concealed spots where lookouts could watch the approaches. A convenient outcrop of rock would serve as the altar surface, the surrounding hillside or woodland as the nave. The Ballymah example sits orientated roughly south-west to north-east, overlooking a river to the west, the kind of elevated, open position that would have allowed a gathered crowd both a view of the surrounding ground and some shelter from the forestry behind. The rock itself is not dressed or modified in any visible way; it is simply the landscape pressed into liturgical service.

The metal cross and Irish-language plaque suggest the site was formally commemorated at some point after the Penal era, a pattern common to many such rocks across Munster and beyond, where local communities later marked spots that had passed into living memory and then into oral tradition. The site sits within forestry, so the atmosphere is enclosed and dim compared to the open hillside it may once have been, and the river to the west remains audible below.