The Castello Barbacane is the squat black-lava fortress on the harbour front of Pantelleria town, and very nearly the only pre-1943 building that survived the Allied bombing intact. It was built by the Normans in the twelfth century, expanded under the Spanish in the sixteenth, and used as a prison well into the twentieth.
The castle is now a small museum with rotating archaeological exhibitions — mostly Phoenician and Roman finds from the island — and the roof is open for the views over the port and the bay. The visit is short (half an hour is enough) and an easy stop to pair with a coffee on the harbour.