Good reminder - I had forgotten about all the steps. The walls are along the top of the castle so yes, it's a lot of climbing. It's been 7 years since my cruise (exactly... I was on the ship at the end of June!) and I still think about it all the time. It was an amazing trip!!
Dubrovnik's city walls are just that - walls that surround the Old Town. They are not on top of a castle: http://www.google.com/imgres?imgurl...f_qVg3JzR1qfM:;wqjQN3yPvYfSlM;Qf_qVg3JzR1qfM: If you plan to walk the walls, do so as soon as you arrive, as they get very crowded and hot as the day progresses.