I would say that you'd want a wide angle to be able to capture the varied combinations of landscape and cityscape, and something bright if you'll be shooting at night. I would say the 28mm 1.8 would do you for an FX camera, or the 16-35mm f4 or 14-24mm f2.8. I'm less sure about the DX lenses having not spent a lot of time with those, but hopefully that gives you an idea.