In the year 818, Diarmaid, abbot of Iona, returned to the island, bringing with him the shrine of St. Columba.[561] This implies that there had been by this time a reconstruction of the monastery at Iona. The same causes which led to the new foundation at Kells being constructed of stone applied with equal force at Iona; and, looking to the time which was spent in erecting the buildings at Kells, which required seven years to complete them, and that four years had elapsed before Diarmaid could bring the shrine to Iona, there can be little doubt that the new monastery there was now likewise constructed of stone. The site, however, was changed. The position of the original wooden monastery was, we have seen, in the centre of the open level ground which extends between the mill-stream on the south and the rocky hillocks which project from the east side of Dunii on the north, and about a quarter of a mile to the north of the present ruins; but of this no vestiges now remain, save the western _vallum_, or embankment, which can still be traced, and the burying-ground near the shore, marked by two pillar-stones about five feet high and three feet apart, across the top of which a third stone lay, forming a rude entrance or gateway.[562] This monastery had never before been exposed to any hostile attack; but, now that it had become the object of the plundering and ravaging incursions of the Danes, it was discovered to be in a very exposed situation. In front was the sea, and behind it, on the west, from which it was separated by the _vallum_, was the lake extending from the mill-stream to the base of Dunii. The ground south of the mill-burn presented a much more secure site, for here it was bounded on the west by a series of rocky heights which could be fortified; and here, where the present ruins of a late Benedictine monastery are situated, can be discovered the traces of older stone buildings, which must have belonged to an earlier monastery.[563] These no doubt may not be part of a stone monastery erected so long ago as the beginning of the ninth century, but the monastery then erected would merely be repaired, and such parts as entirely gave way rebuilt from time to time; and it may be assumed that, when the monastic buildings were once constructed of stone, the monastery would always be preserved in the same place. Here, then, the new stone monastery was probably constructed, consisting of an oratory or church, a refectory, the cells of the brethren and an abbot’s house. Behind the latter is a small rocky hillock called _Torrabb_, or the abbot’s mount, in which is still to be found the pedestal of a stone cross; and on a higher rocky eminence on the west, which overhangs the monastery, are still to be seen the remains of entrenchments and outworks by which it appears to have been strongly fortified.[564] [Sidenote: Shrine of St. Columba placed in stone monastery.]