St Blaise gazes down from the walls of this large free-standing fortress, constructed atop a 37m-high promontory adjacent to the old town. Built to guard the city's western approach from invasion by land or sea, its walls range from 4m to 12m thick. There's not a lot inside, but the battlements offer wonderful views over the old town and its large courtyard is often used as a venue for summer theatre and concerts.
The fort features as the Red Keep in Game of Thrones, making it a bucket list item for serious fans of the TV series.