Cloon Island, now joined more firmly to the surrounding landscape, lost much of its surrounding water as a result of a hydro-electric scheme that lowered the river's level considerably. The effect is quietly disorienting: a place that once had the physical isolation of an island site now simply looks like a low rise of ground, nine acres or so in extent, with the village of Castleconnell visible to the south-east and the Shannon still audible on three sides.

The ruined church on top of the island may date from the twelfth century, though the cross-slabs built into its fabric suggest a community with roots reaching back further into the early medieval period. A cross-slab is a flat stone incised or carved with a cross, often associated with early Christian burial or devotional practice. Writing in 1912, Crawford described this particular example as carved with a Latin cross potent, a form of cross whose four arms each end in a horizontal bar, set within a plain rectangular frame. Okasha and Forsyth, revisiting the site in 2001, noted a second uninscribed cross-slab measuring 65 cm high by 80 cm wide, incised with a Latin cross with expanded terminals, also enclosed in a rectangular frame. That phrase, expanded terminals, simply means the ends of the cross arms flare outward slightly rather than terminating in a straight edge. Between the church ruins and nearby Cloon House, which stands about 20 metres to the south-west, there is also a cross-base with a T-shaped slot cut into it, the purpose and date of which remain unknown.

The site lies roughly 7 kilometres downstream of Killaloe, close to Castleconnell and Doonass. The church ruin commands an open outlook over the Shannon to the south-west, west, and north, which gives some sense of why an early medieval community might have chosen the spot. The slabs themselves are built into the church wall rather than displayed separately, so a careful look at the stonework is worthwhile. The cross-base between the church and the house is easy to miss amid the general scatter of stonework on the site.