>>3293502>taking photos of citydepends you mean people in the city or of buildings? the latter is considered landscape so you will want a lens under 20mm so you can get more in the frame. Avoid going too low as fisheye just looks queer and faddy.
if you take ppl like me you want 16-55mm depending on how close you can get to your subjects and if you want to get environment into the shot as well. I usually just want the subject in the frame mainly so i shoot with a 55mm.