It measures just over five metres long and barely sixty centimetres wide, yet for the Catholic communities who gathered here during the Penal Laws era, it served as an altar. Mass rocks like this one are found across Ireland, products of the seventeenth and eighteenth centuries when the practice of Catholicism was suppressed under a series of legislative restrictions that banned priests, forbade the building of Catholic churches, and made public worship a dangerous act. Congregations moved outdoors, to remote hillsides, cliff edges, and sheltered valleys, using whatever the landscape offered.

This particular rock stands 1.2 metres high and commands an open view northward over the Kenmare River, which would have given those keeping watch reasonable warning of approaching soldiers or informers. Roughly 250 metres to the west lies a natural cave, recorded locally as a hiding place for priests, the figures who were most at legal risk and who moved between such sites with considerable care. The altar itself carries a plain inscribed slab reading "mass rock penal times", and around 1975 a limestone cross was erected behind it, a relatively recent addition that marks the site formally without greatly altering its character. The rock itself remains as it was found, uncut and unworked, its use determined entirely by its shape and position in the hillside.