Sea basin, Orkney Islands , Scotland.
Located off of Scotland's northern tip, the basin is about 15 mi (24 km) long and 8 mi (13 km) wide. Its extensive sheltered waters served as a major British naval base during World Wars I and II. The Germans scuttled their fleet there after World War I. The base was fortified in World War II following German attacks and the sinking of the battleship Royal Oak in 1939. The base closed in 1956.