Kilfenora cathedral, in the Burren parish of the same name in County Clare, holds all three conditions simultaneously, which makes it one of the more disorienting ecclesiastical sites in Ireland. The nave, still in use for worship, retains its 19th-century furnishings and two chimneys from fireplaces inserted during the 1840s conversion, when the chancel arch was blocked up and tall lancet windows punched into the south wall. Meanwhile, the west gable presents something stranger still: a staircase built into the thickness of the wall runs up in front of a two-light window to a small turret, an arrangement that may have served the Sarum rite, a pre-Reformation liturgical tradition in which choirboys sang out through the west window on Palm Sunday.

The site's origins are attributed to St Fachnan, said to have founded a church here in the 6th century, though the earliest hard evidence comes from 1055, when the annals record that the church of Finnabrach was burned during an attack on Murchad O'Brien in Corcomroe. The present structure preserves centuries of subsequent building in close proximity. A lintel from an 11th-century church now rests against the north wall of the chancel, still bearing the square sockets cut for the vertical door posts of the frame it once sat above. The chancel itself dates to the early 13th century and contains a triple-light east window in the Transitional style, its deeply splayed mullions carved with foliage on one capital and a row of four clerics on the other. The diocese of Kilfenora, one of Ireland's smallest, received its status at the Synod of Kells in 1152, and the cathedral reflects the ambition, and the limits, of that modest jurisdiction. The Lady Chapel, not bonded to the chancel wall and therefore a later addition, was converted around 2005 to house several of the Kilfenora high crosses and cross fragments under a new roof of steel and glass, though the raised floor level now leaves some of the chapel's original windows sitting oddly low, almost at ground height.

The porch at the west end of the south wall contains three effigial tombstones and retains a carved bishop's head above the doorway. The chancel, used until the early 19th century and still surviving to roof height, holds a double piscina, a small basin set into a wall used for rinsing liturgical vessels, as well as a sedilia with elaborate tracery and another carved bishop's head above it. Medieval graveslabs and architectural fragments lie on the chancel floor, including the base of what was once a triple-light window.