Mousa

its off the coast of the south east of shetland. You get to it by boat from Sandwick (between Sumbrugh and Lerwick). There is a really nice loch, and stunning views, but most people go to see the Broch. This is what visitshetland.com says about Mousa -

The broch, or fortified Iron Age tower, on the little island of Mousa is the only one in the world to survive almost complete from more than 2,000 years ago, when it was built as a refuge against raiding local tribes. Mentioned in the sagas as a refuge for an eloping couple, Mousa Broch is one of the wonders of European archaeology – and also ornithology. Storm Petrels nest in its stone, visiting the broch only at night. A night excursion to the broch, to hear their eerie calls, is an experience not to be missed.

In daylight, Mousa abounds in other wildlife: a large colony of Common and Grey Seals basks around an inlet on the east side of the island; there’s a chance you may see an Otter (Dratsi, in Shetland dialect); Fulmars (Maalies) and Black Guillemots (Tysties) are very common; and Great Skuas (Bonxies), Arctic Skuas (Aalins) and Arctic Terns (Tirricks) defend their nesting grounds by dive-bombing all intruders, humans included – so try to walk around the breeding colonies, not through them, for their sakes and yours.