What draws less attention is a set of ghostly timber footprints in the soil, the traces of a structure so small it could fit inside a modest garden shed, yet one that quietly complicates the usual story of Irish Christianity.

During excavations on the island in the 1970s, the archaeologist de Paor uncovered traces of a small rectangular timber building, roughly three metres by two, aligned north to south and sitting within a rectangular palisaded enclosure, that is, a precinct defined by a fence of upright wooden stakes. At the southern end of the building were the traces of a pillared portico, a small colonnaded porch-like entrance. Both the building and its enclosure appeared to have been rebuilt several times over, suggesting a structure of some importance and longevity, and it is possible that it was eventually replaced by the nearby stone building known as the Confessional, which stands only about ten metres to the south-east. The structure was interpreted as a Christian shrine, but its form is not straightforwardly Irish. Scholars recognised in it a type of shrine-within-enclosure familiar from Gallo-Roman and Romano-British religious contexts, the kind of small sacred building set apart within its own defined precinct that was common across late antique Gaul and Roman Britain. The larger, southern portion of the enclosure lay beneath the medieval Saint's Graveyard and was never fully excavated, meaning the full extent of the original complex remains unknown.

What the site offers, then, is a reminder that early Irish Christianity did not develop in isolation. The monks and communities who settled on islands like Inis Cealtra were heirs to a much wider late antique world, and the forms they used to house the sacred carried memories of that world with them, even when translated into timber on a small island in an Irish lake.