The star-shaped Renaissance citadel that gives the town its silhouette covers about 12 hectares on the slope above the bay. Inside the walls you can walk through the layered history of the site: the Greek settlement of Rhode, the Roman town that succeeded it, the medieval Lombard monastery of Santa Maria, and the sixteenth-century military complex itself.
The site has an informative on-site museum with finds from the Greek and Roman levels, including coins, amphorae, and the remains of a small wine-making facility. Allow two hours for a thorough visit. Buy the combined ticket if you also plan to see the Castell de la Trinitat across the bay.