As I said before, if you're visiting Dubrovnik, make sure to climb and circumnavigate the walls. It provides a great perspective of the Old City. Suddenly, you're on top, gazing on the rooftops of the buildings and houses inside.
The walls are actually protected by fortresses on strategic areas, which form part of the overall structure. There are several of them, positioned in various places around the Old City.
Some of these fortresses are open to climb, which provide further views of the inland, as well as the sea, depending on which fortress you are in.
See the Onofrio Fountain from above? Or how about the churches and the tall buildings, that from the ground they appear very massive, but from he walls you seem to be just wading through them? Like I said, this is an interesting perspective of the city, which I definitely recommend.