Scalloway Castle
This waterfront fortress was built in 1600 by Patrick Stewart, Earl of Orkney and Shetland. "Black Patie," as he was known locally, was hanged in 1615 for his cruelty and misdeeds, and the castle was never used again. To enter, retrieve the key from the Scalloway Museum during opening hours; you can then explore these handsome ruins to your heart's content.