Yet that arch is very nearly all that remains legible at the old church of Kilcullane, a nave-and-chancel structure whose east gable had already been reduced to little more than a metre in height by the time anyone thought to measure it carefully. Every window in the building has lost its form entirely, and the stretch of south wall where the doorway once sat has been destroyed to the foundation. The walls that do survive run to around three metres high and are built of regular-sized limestone set in lime and sand mortar, a solid enough construction that has nonetheless spent centuries losing the argument with the elements.

The name carries its own quiet archaeology. Scholar T.J. Westropp, writing in 1904 to 1905, traced the place name back through a sequence of documentary forms: Kilcallane in 1578, Kylkyllane in 1586, and, in the Irish, Cillcaclain, meaning Cathlan's Church, with the local pronunciation recorded by the nineteenth-century scholar John O'Donovan as Kilkillaun. The site appears in a charter as early as 1185, described in relation to a ford and a marsh, and in 1607 the lands of Kilkellan were granted to one Edward Browne by patent. By 1657, when William Petty's Down Survey was being compiled, the church was already depicted as roofless with only one gable standing. That same survey, drawn up between 1654 and 1657, shows the church and Kilcullane Castle side by side on the parish map, the two structures occupying their respective positions as they presumably had for generations.

The ruins sit on the north side of a small graveyard, with Kilcullane Castle roughly 110 metres to the east, beyond which the River Camoge runs close by. The graveyard was described in 1840 as not much used, and there is no particular reason to think that has changed. The choir arch, pointed in style and formed of brown cut stone, is the feature most worth finding; it marks the division between the nave and the chancel and gives a sense of the building's original ambition even as the rest of the fabric has subsided around it. The site lies on level ground in the townland of Kilkillaun, and the proximity of both a castle and a named river makes orientation relatively straightforward for anyone arriving with an Ordnance Survey map or its digital equivalent.