Wowee Susan!
Years ago I used to run the stairs at a dam down the road, it was something around 105-120 steps I seem to remember, and my legs would be WRECKED if I did it even three times. Then I did some short runs when we visited Venice a couple of years ago, most of the sidewalks and almost all of the bridges are granite, that stuff is HARD.
It sounds like a beautiful place to run but really, really tough, so you should be proud of doing it at all, WITH stops to catch your breath.
Speed comes from what you put behind you. - Judi Ketteler