On the island of Mousa, off Sandwick, this prehistoric fortified house, dating from some 2000 years ago, is an impressive sight. Rising to 13m, it’s an imposing double-walled structure with a spiral staircase to access a 2nd floor. It has featured in Viking sagas as a hideout for eloping couples. In its walls nest hundreds of storm petrels, whose return to the nest at dusk is a stirring sight.