If I could only take one of those three for city shots that includes structures and monuments, I'd personally take the 18-55. I shoot a lot of cityscapes, bridges, and so forth, and I use the wider end of my lenses a lot more than anything else for that sort of thing, otherwise it doesn't fit until I get so far away that I can't get a shot because there's too much other stuff in the way.
I refuse to travel that light (one lens) and limit myself though, so it's not something I think much about. When an opportunity presents itself, I like to be able to reach into my bag and pull out the appropriate tool for the job and get to work.