The castle that gives Delvina its strategic importance stands on the high ridge above the modern town. The first fortifications were probably Byzantine, expanded and refortified by the Despotate of Epirus in the 13th century, and rebuilt again by the Ottomans, who used it as a regional administrative centre for several hundred years.
What remains today is principally the curtain wall, several towers, and a few ruined buildings inside; the walk up takes 15-20 minutes from the centre of town, and the view from the top — out across the Vrina plain to the sea on a clear day — is the main reward.