At the west end of a church in Castledermot, County Kildare, sits a small granite vessel that is easy to overlook and quietly puzzling once you stop to examine it. Rectangular and roughly shaped, it measures about half a metre long and less than thirty centimetres tall, with a shallow, sloping-sided basin scooped into its upper surface. That basin is only twenty-two centimetres across, and there is no drainage hole. It now rests on a modern pedestal, which gives it the slightly incongruous air of an exhibit in a very small museum.

The object is a piscina, a liturgical basin traditionally used in Catholic and medieval Christian practice for rinsing the chalice and the priest's fingers after Mass, with the water draining away through a hole directly into the earth rather than into the general drainage system, keeping consecrated water separate from ordinary waste. This particular example breaks that rule: it has no such drain. Whether the hole was never cut or has simply been lost is not recorded. The stone itself is granite, a material in common use in the Kildare and Carlow region, and its rough shaping suggests either great age or a relatively modest original context. The church to which it belongs, a medieval foundation in Castledermot, sits in a town long associated with early Christian settlement, and the vessel was noted in a 1986 survey of the area's medieval remains.