Castledillon, situated on the south bank of the River Liffeyopposite Straffan, is an ancient monastic site in its own right founded by Iollathan of the desert (feast day listed as 2 February in the Martyrology of Tallaght) and accorded a genealogy which indicated close kinship with the Uí Dúnlainge kings of Leinster. By 1294 the church of Tristeyldelane was described as "not worth the services of chaplains" in the Calendar of Christ Church deeds. The site is now identified by a pile of stones and one headstone, erected in 1758 to the Spellissy family. The Castledillon Friars Stone, probably erected for a 15th-century abbot of St Wolstan's (four miles to the east), remained on the site until removed to the Visitor centre in Kildare town.