we would see the Sun on his journey, crossing between the building tops from our side over to the RPO Building side.
Does it simply mean "roofs"? So why "tops" and not "top"? Or why building and not buildings?
Could you explain it to me?
The fuller text:
when we were new, Rosa and I were mid-store, on the magazines table side, and could see through more than half of the window. So we were able to watch the outside – the office workers hurrying by, the taxis, the runners, the tourists, Beggar Man and his dog, the lower part of the RPO Building. Once we were more settled, Manager allowed us to walk up to the front until we were right behind the window display, and then we could see how tall the RPO Building was. And if we were there at just the right time, we would see the Sun on his journey, crossing between the building tops from our side over to the RPO Building side.