For anyone interested in ancient history, there are ruins very near Cagliari. They are Roman ruins built on top of an ancient Carthaginian/Phoenician trading post. The site has been well excavated with pleasant walking paths and it is situated right on the sea, so also very scenic. (In fact some of the ruins are under water, and I understand that in summer you can do a snorkeling tour to see them.)   It's pretty easy to get there by local bus/shuttle, or perhaps your cruise line will o