Within the landscaped grounds of Furness House in County Kildare, a disused graveyard contains a medieval church whose walls still stand to virtually their full original height, retaining patches of old plaster and framed by windows and doorways cut from tufa, a lightweight volcanic stone favoured by early medieval builders for its ease of carving. What makes the structure quietly puzzling is a structural detail that only becomes apparent on close inspection: the nave and chancel, though they appear to form a single coherent building, are not bonded to one another. The masonry of the two sections was built independently, which suggests that the chancel may have been added to an earlier, possibly pre-Norman nave, rather than constructed as part of one original design.

The building is tentatively dated to the late twelfth century and is built from roughly coursed limestone flags, with walls averaging around 0.9 metres thick. Its plan is straightforward: a nave of roughly 9.8 metres in length connected to a smaller chancel by a round chancel-arch, also of tufa. The west gable is pierced by three graduated lancets, and opposing narrow windows light both the nave and chancel, each square-headed on the outside but opening into a wide internal splay with a round head, a typically Romanesque arrangement. A piscina, a small stone basin set into the south wall of the chancel and used in Catholic liturgy for disposing of water used in sacred rites, is still visible. Beneath the chancel floor lies the Nevill family vault, once reached by steps from the nave. In 1210, according to a record cited by Synnott, a figure named Richard de Lesse granted the church and its tithes to the Abbey of St. Thomas in Dublin, and the building was still functioning as a parish church in the mid-seventeenth century. Glazed tiles and slates found within the chancel point to some form of renovation during that later period. Inside the nave, a granite font and a possible early Christian cross-slab, a carved stone marker of a type associated with early Irish ecclesiastical sites, add further layers to a building whose history spans several distinct phases. The church was stabilised by the Office of Public Works in 1968 and is now a National Monument in State care.