In a field in County Kildare, cattle wander freely through a graveyard. There is no fence, no gate, no boundary to speak of beyond the ragged remnant of a D-shaped earthen bank, roughly 52 metres across, whose concrete posts have mostly toppled. What remains inside is a fragment of a wall, the last visible piece of a church that once stood here, and a scattering of graves marked by rough stones broken from the former building itself. One exception stands out: a single well-cut headstone bearing the name Spellicy and the date 1758, still upright just inside the eastern bank.

The place has a longer history than that lone legible stone suggests. Castledillon was originally known as Diseart Iollathan, meaning St. Illan's Hermitage, a diseart being a type of early Irish monastic retreat or hermitage associated with a single holy figure. The saint in question, Illan, was venerated on the 2nd of February. Over time the name corrupted, passing through forms like Tristledelan before becoming Castledillon entirely. The D-shaped enclosure, with its straight western side running some 61 metres, is thought to be an early ecclesiastical enclosure, a form of boundary that in Ireland often predates Norman church architecture by centuries. Within it, to the south of the church site, a cluster of small uninscribed field stones points to what may be a children's burial ground, a cillín in Irish tradition, used for unbaptised infants who could not be buried in consecrated ground. The enclosure was also the original location of the Castledillon Stone, a 13th-century carved effigy of some quality, now removed from the site.

Access to the enclosure is possible through several gaps in the surviving bank, with the original entrance thought to have been on the northern side. The graves visible today are concentrated in a small southern area, and the mixture of rough improvised markers and the solitary cut headstone gives a clear sense of a site that has been quietly sliding out of use and memory for a long time.