The building at Ballylannan sits on a low bluff where the Owenduff and Corock rivers meet, their combined waters flowing south past the old Anglo-Norman settlement of Clonmines and on into Bannow Bay. What survives of the church is modest, barely two and a half metres high, but its survival owes less to neglect than to a deliberate act of repurposing: in 1824, the Leigh family of Rosegarland consolidated the crumbling walls and attached a tower with an entrance to the south side, converting the shell into a private mausoleum. The result is a structure that reads as neither quite a church nor quite a monument, but something in between.

Almost nothing of the original medieval fabric remains visible. Two features in the north wall, a pointed doorway and a small window, both now blocked, are the only surviving elements from the church's earlier life. The rectangular graveyard surrounding it, roughly forty-five metres east to west and thirty metres north to south, is enclosed by masonry walls and contains at least one object of considerable antiquity: a bullaun stone, a roughly worked boulder with a deliberately hollowed basin cut into its surface. Bullaun stones are found at early ecclesiastical sites across Ireland and are thought to have served ritual or votive functions, though their precise use is still debated. This example is small, around half a metre in length, with a single oval basin about eight centimetres deep.