Prioritise Dubrovnik, then leave time to breathe
1. Walk the City Walls at opening or late afternoon. This is the one activity to plan around: the circuit takes about 1.5 to 2 hours and has stairs, little shade and no useful shortcut once you are committed. Buy from the official City Walls or Dubrovnik Pass channel and check that day's entry hours; the ticket/pass arrangements can change seasonally. Entering at Pile Gate is simplest for most visitors. Bring water, and do not schedule it immediately after a large lunch.
2. Keep the Old Town route short and specific. From Pile Gate, walk Stradun, detour to the Rector's Palace and Cathedral, then climb one side street for the view back across the roofs. The streets are public and free; museums are the paid choices. One unhurried morning or evening is enough to understand the layout. Use the Dubrovnik eating guide to place lunch away from the busiest part of Stradun.
3. Choose Lokrum for an easy half-day, not a rushed checklist. Boats leave from the Old Port in season, and the crossing is short, but allow time for the return queue and the walk to the swimming spots. Take water shoes if you plan to swim; rocky entries are normal on the Adriatic. Check the current boat timetable and island opening arrangements before you head down to the harbour.
4. Use Mount Srđ for the view, but pick your transport honestly. The cable car is the straightforward option when it is operating; the hike is steep, exposed and much longer than a casual stroll. Go late in the day if heat is an issue, but leave enough time to return before dark if walking. If you want a day away from the city, Ston combines walls, salt pans and oyster country; it needs a bus, car or organised trip, not a spare hour. Stay near the right gate or bus corridor with this area guide.