The body of water known as Scapa Flow is situated in which island group?

Scapa Flow is a body of water in the Orkney Islands, Scotland, sheltered by the islands of Mainland, Graemsay, Burray, South Ronaldsay and Hoy. Its sheltered waters have been used by ships since prehistory and it has played an important role in travel, trade and conflict throughout the centuries.

A consultation in ballast water management in 2013 measured the commonly used Harbour Authority definition of Scapa Flow at 324.5 square kilometres (125.3 sq mi) and just under 1 billion cubic metres of water.

Scapa Flow has a shallow sandy bottom not deeper than 60 metres (200 ft) and most of it about 30 m (100 ft) deep, and is one of the great natural harbours/anchorages of the world, with sufficient space to hold a number of navies.

Vikings anchored their longships in Scapa Flow more than a thousand years ago, but it is best known as the site of the United Kingdom's chief naval base during World War I and World War II. The facility was closed in 1956.