A bullaun is a large stone, usually boulder-sized, with one or more deliberately carved or ground circular depressions in its surface. The hollows collect rainwater, and that water has long been considered curative or sacred. Nobody is entirely certain when most bullauns were made, nor always why, though they are associated with early Christian and pre-Christian ritual practice, and many are found near old church sites, holy wells, or monastic enclosures. The one at Fomerla is recorded as a monument in its own right, which suggests it retains enough of its original form to be recognised as significant.