Corfu 491 00, Greece
Old FortressThe "old" fortress dates back to Byzantine times, but the structure is mostly Venetian. Sitting on a promontory off the old town of Corfu, it is reached by a bridge over a sea canal and is famously impregnable, resisting not one but three separate Ottoman sieges. The views from the walls are well worth the trip, and include the incongruous church of St. George. Built by the British, and looking like a old Greek temple, the church is one of the postcard images of the island.