Scapa Flow is a body of water in the Orkney Islands, Scotland, United Kingdom, sheltered by the islands of Mainland, Graemsay, Burray, South Ronaldsay and Hoy. It is about 312 sq km (120 sq mi). It has a shallow sandy bottom not deeper than 60 m (200 ft) and most of it about 30 m (98 ft) deep, and is one of the great natural harbours/anchorages of the world, with sufficient space to hold a number of navies. Viking ships anchored in Scapa Flow more than 1000 years ago, but it is best known as the site of the Royal Navy's chief base during World War I and World War II. The base was closed in 1956.
Scapa Flow was the main port of the British Home Fleet, and the pride of the United Kingdom.
In January 1941, as an act of retaliation for the Big Switch of 1940, the Soviet Air Force based out of Murmansk launched a hit and run raid on the harbour, fleeing before the RAF could give chase. Radio Moscow claimed the raid inflicted heavy damage while a Royal Navy spokes man was quoted in The Times as saying these claims were "greatly exaggerated."