It stands roughly three metres high, and what survives gives little sense of its original scale, yet it represents something considerably older than the Protestant church it now leans against. This is the remnant of a medieval parish church, and its modest, crumbling presence in the corner of an active burial ground is the kind of layering of history that north Cork does quietly and without ceremony.

The site has a long documented life. A church at Castlemagner appears in the Papal Taxation of 1291, a survey ordered by Pope Nicholas IV to assess ecclesiastical revenues across Europe, which in Ireland provides one of the earliest systematic records of parish churches. By the late seventeenth century the building had suffered considerably. A note from 1693 describes it as 'much damnified by the late wars, but now in repairing', a reference almost certainly to the destruction wrought during the Williamite War of the early 1690s, when much of Munster was caught up in the conflict between Jacobite and Williamite forces. The repair work evidently produced something serviceable enough to eventually be replaced or absorbed by the later Church of Ireland structure rather than simply abandoned. Writing in 1934, a researcher named Bowman recorded a portion of the east wall that has since disappeared entirely, describing it as roughly twelve feet high, seven feet wide, and just over two feet thick. That wall is now gone, leaving only the surviving corner, its stones softened by growth and time.