Ordnance Survey letter-writers in the 1840s recorded a carved stone set into the wall above the entrance, depicting a cat with two tails, attributed in local tradition to the Gobaun Saer, a semi-mythological craftsman-saint who appears across Irish folklore as the builder of impossible things. By that point, the stone was already gone. According to the same account, it had been taken by carmen from Cashel and carried off to Holycross. What remains of the tympanum, the carved panel that would have filled the space above the doorway, is largely broken out, its decorative elements missing. The doorway itself survives in better condition: three richly worked orders carrying roll-mouldings, chevrons with beaded ornament, and vegetal carving, framing an entrance that now opens onto roofless limestone walls and a medieval graveslab lying on the nave floor.

The church was dedicated to St. Farannan, who, unusually for an early Irish saint, left Ireland altogether, dying in 982 at a place called Valcoidon on the Meuse, later renamed Waser. The building that carries his name is a nave-and-chancel structure, the walls and steep gables surviving to a considerable height, built from limestone rubble with sandstone used for the architectural details and quoins, the dressed corner stones that give a wall its angles and stability. The chancel, compact at roughly two and a half metres square internally, is barrel-vaulted and retains a rectangular aumbry, a small wall recess used for storing liturgical vessels, in the north wall. Above the chancel there was once a hidden chamber, accessible from the nave, probably by a wooden stair in the north-east angle, that led to a doorway set above the chancel arch. The chancel arch itself has largely collapsed, though its engaged columns survive with decorated capitals and bases. A small stoup for holy water is set into the nave wall just south of the entrance, and patches of the original internal render still cling to the walls. The site became a National Monument in 1883, when the Commissioners of Public Works undertook repairs under the architect Sir Thomas Deane. Earthworks survive in the adjoining field to the north, suggesting the church did not stand alone in the landscape.