Broch of Mousa (or Mousa Broch) is a preserved Iron Age broch or round tower. It is on the island of Mousa in Shetland, Scotland. It is the tallest broch still standing and amongst the best-preserved prehistoric buildings in Europe. It is thought to have been constructed c. 300 BC,[1] and is one of more than 500 brochs built in Scotland

Mousa is a small, treeless island of open grassland and heath typical of the Shetland landscape. Its rocky coastline includes small natural inlets that provide landing places for boats.[5] Immediately beside the broch lies the sheltered tidal basin known as the Loch of Mousa, which connects to the sea through a narrow channel.[3]

It is built of dry stone with no mortar.[11]

Mousa Broch continued to be used over the centuries and is mentioned in two Norse Sagas. Egil's Saga tells of a couple eloping from Norway to Iceland who were shipwrecked and used the broch as a temporary refuge.[14] The Orkneyinga Saga gives an account of a siege of the broch by Earl Harald Maddadsson in 1153 following the abduction of his mother, who was held inside the broch.[14]

https://en.wikipedia.org/wiki/Broch_of_Mousa