Anne Ross, a respected authority on the subject, describes the beliefs and practices of the Celts: “The priests, the Druids, were believed to have carried out their ritual practices and to have made offering to the gods only in natural places, without structures—in groves of trees made sacred by long association with the gods, for example, or beside sacred wells whose waters contained distinctive virtues and through which access to the patron deity could be gained.”—Everyday Life of the Pagan Celts, page 136.
... We could picture those pagan Celts gathered at such a spot seeking favour from their gods.