Dubrovnik

Dubrovnik can be seen in a day: its complete medieval walls, walkable in a 2km loop, and the old town within them fit into that time. May-June avoids the heat and July-August crowds, when several cruise ships arrive daily. It's among the priciest destinations on the Adriatic coast, with prices spiking in high season due to its international fame. Its walled old town, a UNESCO World Heritage Site, was a real filming location for King's Landing in Game of Thrones, which multiplied its tourist numbers over the past decade.