For centuries, political and religious power in Orkney centred around a small tidal island off the north-western corner of the Mainland. This island goes by the name of the Brough o' Birsay.
With an area of 21 hectares, the Brough is separated from the Point o' Buckquoy on the Mainland, by the waters of Brough Sound - a distance of approximately 240 metres (262 yards).
Access to the Brough is, therefore, restricted to a few hours each day, at either side of low tide, when a causeway across is clear. This not only meant the island had a prime defensive position, but was also an ideal base for sea travel south, north and east
Find out more: http://www.orkneyjar.com/history/broughofbirsay/