These enclosures, typically defined by a curving boundary of earth or stone, were the precinct walls of early medieval religious communities, enclosing a church, burial ground, and sometimes the cells of monks or anchorites. They tend to predate the parish system that reorganised Irish Christianity from the twelfth century onward, and their circular or oval outlines frequently endure in the shape of later field boundaries or graveyards long after any standing structure has vanished.