They may be regarded as the very latest class of prehistoric strongholds, reaching their greatest development in early historic times, and surviving through the Middle Ages
In Scotland and Ireland, an artificially constructed site for a house or settlement, usually on an islet or in the shallows of a lake. Made of timber or sometimes stone, crannogs date from the Late Bronze Age into the Middle Ages. Usually fortified by stockades, they were among the latest prehistoric strongholds. See also Lake Dwellings
{i} crannoge, artificial or natural island built in a lake or swamp in prehistoric Ireland and Scotland; lake residence or fort built on an artificial island in ancient Ireland and Scotland