The shallow circular depression is still visible on its surface. It is the kind of quiet, pragmatic reuse that tells you something about how a building was worked and reworked over time, with older pieces absorbed into later fabric without ceremony.

The church sits on a low ridge in undulating pastureland, in the centre of a graveyard, and what visitors see today dates largely to the late 15th or early 16th century, though the site itself is considerably older. It appears in the Papal Taxation List of 1302 under the name Killadlagh, rendered in Irish as Cill Eidlach, and again in the Calendar of Papal Letters in the early 15th century. Its original foundation has been attributed at various points to Saint Falie or Falia, and to Saint Lonan, with no settled consensus. The structure comprises a long rectangular nave with a square transept added against the eastern end of the south wall, probably around 1500, and a subtle offset in the north wall may record precisely where the original nave ended before that addition was made. The east gable, which was described in 1839 as carrying a tall round-headed window of impressive dimensions, collapsed in a storm in 1903 and only a small ivy-clad stub survives; excavation in 2013 located the altar at this end. The transept windows are worth attention: ogee-headed loops with finely carved jambs and decorated spandrels, and a twin-light opening in the south wall that retains its hood-moulding though its central mullion is gone. The arch connecting nave and transept carries chiselled and pecked ornamental patterns on its voussoirs, the wedge-shaped stones that form the curved span. Elsewhere in the walls, a fragment of a quern stone and an inscribed stone carved with a vine leaf and a lion in false relief have been built in as ordinary rubble. A burial vault dated 1784, belonging to the Thynne family, occupies the north-west corner of the interior, which is otherwise overgrown and scattered with loose cut stone, including the base of a font near the west wall.