Bronze Age remains are some of the most extensive in the North-Western Highlands, particularly at the western end of the island; these include fragments of huts arranged in circles, and ancient field walls, as well as pottery artefacts from the Beaker Culture. In the Iron Age a hillfort - Dun Channa - was constructed at the far western edge of Canna; another was probably constructed at the eastern edge, at Coroghon, in the same period. In the 6th century, when the Irish missionary Columba first sailed to Iona, he first arrived at the island of "Hinba", which he later treated to as a place of contemplative retreat. The extensive early Christian sculptures and structures on Canna, and its traditional association with Iona, have made many consider it to be the otherwise unidentified "Hinba". However, Adomnán (the chronicler of the life of Columba) noted that Brendan the Navigator stopped at "Hinba" while travelling from Ireland to Iona; Canna is a most unlikely landfall on such a journey as it is well beyond the destination. At Keill are two large richly decorated Celtic crosses, dating from the 8th to 9th centuries, which are thought to attest to the presence of a monastery. A cursing stone, was located at the site; a device normally associated with Ireland, this only the second cursing stone ever to be found in Scotland. On the south coast of the island are the remains of a small, isolated, cashel-like building, which would have been difficult to supply with provisions, except by sea. In Gaelic the site is known as "Sgorr nam Ban-naomha", meaning ""grassy slope of the holy women""; in the 19th century, local people believed it had once been a nunnery, but it is now thought to have been a hermitage, associated with the monastery at Keill. The enclosure contains three carved stones, bearing crosses, and was once believed to have had a healing spring. Following raids by the Vikings in the 9th century, the Hebrides became part of the Kingdom of the Isles, a Norwegian crown dependency also known as "Suðreyjar" (the "Southern Isles"). Written records are few, but the Viking occupation of Canna is evident from place names such as the element "sgor", "gearaid" (enclosure), "tota" (homestead) and Sanday ("sand island") (though the name "Canna" itself may pre-date the Norse period).