As with Columba, who was born in Donegal, many of the early Celtic clergy arrived as settlers from Ireland, with their communities of missionary monks, many of them trained at Iona, carrying the good news far and wide – as far, indeed, as Germany and Switzerland, as well as throughout Scotland. St Aidan established his monastery at Lindisfarne in the 630s, going on to convert the Angles of Northumbria and establish the monastery at Melrose, whence St Cuthbert proselytised throughout Lothian. From this period dates some of Scotland’s most characteristic imagery, in the form of Celtic crosses and similar designs in stone and metalwork. Following the Synod of Whitby, however, called by the king of Northumbria in 664, the Roman model of Christianity achieved dominance over the Celtic version, leading to the rapid decline of the Columban church, hastened further by Viking raids on Lindisfarne and Iona in 793 and 795.