COUNTY MAYO, IRELAND—A survey of the rocky island of Caher has identified an outer arc of altars or “leachts” that marked a station on a medieval maritime pilgrimage circuit. According to archaeologist Michael Gibbons, the circuit “represents a now rare example of a form of religious devotion stretching back at least a millennium on Ireland’s Atlantic coast.” The island is home to a monastery with a late medieval chapel; a series of stone crosses and small stone altars; a holy well; and a wall chamber where pilgrims or monks confined themselves in solitude.  The island was abandoned in the early nineteenth century.