The exception that draws the eye sits apart, close to the highest point of the island, and carries a name that explains its isolation: Clogás an Oileáin, the bell tower of the island. A working bell tower needed height and a clear line of sound across water, and whoever built or adapted this structure understood that.

The core of the building is a 13th-century church of roughly coursed limestone, measuring just over eleven and a half metres east to west. Both gables survived to their original height, and the four-storey tower at the north-west end is bonded into them, a detail that has complicated attempts to date the tower independently. One reading, advanced by the architectural historian Roger Stalley, holds that the tower is a later addition that absorbed the apex of the pre-existing west gable. The bonding, however, suggests the two elements may be contemporary, or that the church was substantially remodelled, probably in the 15th century, when the tower and a two-storey priest's residence at the west end appear to have been added or formalised. The chamfered jambstones of two doorways near the west end of the interior, one leading to a mural staircase that accessed the upper floors, are consistent with 15th-century work. An aumbry, a small wall recess used to store liturgical vessels, survives in the east wall, and a second is visible in the north wall. The tower floors were timber throughout, carried on wall plates whose beam holes remain visible at each level. The south walls of both church and tower were in poor condition before the Board of Works undertook repairs in 1882 to 1883, by which point the south-east and south-west angles had been robbed of their stone and only the wall footings of the south wall remained. A 19th-century photograph records the state of the ruin before that intervention.

Inchcleraun is accessible by boat from Lanesborough or Ballyleague, and the island is grazed pasture rather than managed heritage site, so the ruins sit in open ground without interpretation. The Clogas building stands separately from the main enclosure to the south-east, which means a visitor who heads directly for the cluster of churches near the shore may not immediately notice it. It is worth seeking out as its own destination, particularly for the intact gables and the visible beam holes in the tower walls, which give a clear sense of how the timber floors were once suspended inside the bare stone shaft.