A small medieval tower in an overgrown graveyard near Naas presents a quietly disorienting structural puzzle: it is square at ground level and round at first-floor level, a shift in geometry that sits beneath a stone roof and says very little about itself to anyone who manages to push through the surrounding vegetation. The tower now abuts the west end of an eighteenth-century church, which was itself built over the levelled nave of a medieval predecessor. At some point, the tower's original north doorway was blocked up and a vaulted roof inserted, converting the ground floor into an entrance porch for that later church. A second doorway in the east wall opened directly into the church, while the east wall above it remained open to first-floor level, looking into what had once been the medieval nave. A drawing made by Beauford in 1789 shows a partially ruined parapet that no longer survives.

The site's history reaches back considerably further than either church. According to Killanin and Duignan, this is the location of a church founded by Bishop Auxilius in the fifth century, one of the bishops traditionally associated with Patrick's mission to Ireland. Abbots of Killashee are recorded in the Annals from 829 AD, suggesting a monastic community of some continuity here through the early medieval period. A souterrain, an underground stone-lined passage typically associated with early ecclesiastical or settlement sites, survives in the adjoining field to the south-west and was probably connected to that original foundation. The tower itself is built of rough, uncoursed granite blocks with walls estimated at around 1.25 metres thick at the base, and it may have served as the semi-fortified residence of the local cleric rather than as a purely ecclesiastical structure. On the east wall, the scar of the roofline of the vanished medieval church is still visible, a faint geometric ghost pressed into the stonework that quietly maps what was once there.