People lived on the island in Neolithic times, and traces of their hut circles remain. During the 5th century the island became a place of refuge for Christians and a small Celtic monastery existed. In 516 Saint Cadfan arrived from Brittany and directed the building of St Mary's Abbey. In medieval times three pilgrimages to Bardsey Island were said to be equal to one visit to Rome. In 1188 the abbey was still a Celtic institution, but by 1212 it belonged to the Augustinians. Many people still walk to Aberdaron and Uwchmynydd each year in the footsteps of the saints. Only ruins of the old abbey's 13th-century bell tower remain. A Celtic cross in the ruins commemorates the 20,000 saints claimed to be buried on the island.