A piscina or sacrarium's a shallow basin placed near the altar of a church, used for washing the communion vessels. They're often made of stone and fitted with a drain, and are in some cases used to dispose of materials used in the sacraments and water from liturgical ablutions. They're found in Roman Catholic, Anglican, and Lutheran churches, and a similar vessel's used in Eastern Orthodox churches. History The piscina's a Latin word originally applied to a fish-pond, and later used for natural… (More on Piscina)