I feel you're off to a great start. The values could use a bit of work. I'm getting you were going for a simplified scale of values, but more could be done to draw in the eye of the viewer- even with limited values. After reading your description, and seeing "modern city" i realize this is why these may have fallen short of their full potential. To me, these concepts feel very traditional and not set anywhere in the future, nor do they have clean simple lines that are modern. If these were revisited with a greater focus on the modern aspect, these concepts could grow and be pushed further. Keep up the good work, but always challenge yourself and the concept at hand.