I early June I spent two weeks in Greece, including a week on a large sailboat, The Star Flyer.  We cruised the islands, perhaps the most interesting was Santorini, the town of Threra had been overwhelmed in a volcanic eruption about 1620 BC.   It was preserved like Pompeii  and excavated in the past century.  Athens was very crowded but the old ruins, like the Parthenon are wonderful.
The Star Flyer
The Parthenon