Dubrovnik is one of the best preserved medieval, walled cities in the world. Inside the city are delightful narrow streets, churches, synagogues, and squares. However, the best way to appreciate Dubrovnik is atop its walls.
The citizens relied on its high city walls for defense by land and by sea. Walking the full 2km circuit you not only get a chance to view the city from all angles, but also the beautiful Adriatic Sea, the islands that run along the shore, and the neighboring towns.
This shot was taken looking South toward Cavtat, a lovely town 20 minutes outside of Dubrovnik that I recommend spending a day in or making your home base to explore the region.
Here's two tips.
1. Drink plenty of water, especially in the summer. It can get very hot on the walls, which are without much shade. You can fill your water bottle at the fountain near the front gate.
2. Find out when the cruise ships dock and avoid visiting on those days to escape the crowds. Ask around or drive by the docks to see if they are in port. If they are, try to arrive very early in the morning or much later in the afternoon.