off the shores of Scotland
Iona became one of the last bastions of Druidism, as Druids retreated there beginning with the invasion by the Romans.
Columba (saint) eventually went over, set up a monastery (Not a conventional monastery. Monks could be married.) and began to convert the masses of Iona.
Iona is chiefly a tourist destination now, with many Christian sites and the remains of Druidic Cairns.
Webster has this to say about it,
Usage: geographical name
Island near Scotland in S Inner Hebrides off SW tip of Mull Island area 6 square miles (16 square kilometers), population 120.