Crannog, named after cran, the Irish for tree, is an artificial, man-made island which was sometimes linked to the shore by a stone causeway or timber gangway.

They were constructed with split timber covered with layers of soil, brushwood, peat and stones and circled by a wooden fence.

As with raths, considerable manpower was needed to build them, and therefore these were dwelling-places for the affluent and were designed for defence.

They were probably the centres of thriving farms whose occupants lived in this easily-defended location to protect themselves and their livestock from passing marauders.

The entire encampment would have consisted of a farm house, with cattle and crops being tended in nearby fields.

Local woodlands would have provided the homestead with fruit, hazelnuts, vegetables and medicines, as well as meat products such as game and wild boar.

Some crannogs may even have served as the equivalent of a holiday home for the wealthy where recreations such as fishing, wildfowling and hunting could be carried on.

The fact that many crannogs now lie submerged has helped archaeologists as the water-logged conditions preserved many perishable items such as wooden bowls and cups that would have been destroyed on land.