1st and 3rd photos are interesting. I'm not liking the 2nd so much for a few reasons. First, either a very high ISO (can't see the EXIF info) was used or the cam has a processing issue, because the "banding" (concentric rings) are really distracting. There is also quite a bit of noise in that photo. It would also appear as though a lens hood was used that was too long for the focal length of your zoom, causing the darkened corners. These are all technical issues; the composition on that 2nd photo is also bland and symmetrical - I would include a bit more of the skyline or rooftops to give it some sense of the urban landscape and move things over to one side or the other just a bit.
The 1st shot is quite nice! It has beautiful colors, sharp bird silhouettes in flight and a well-placed horizon line.
I'd go back and shoot that third photo again, but change my position and try it at different times of the day. Shooting it at a parallel or 180 degree position tends to show the surface features as shapes rather than revealing what is probably some interesting form. Try some different angles so that the sun has a chance to reveal the relief, using a combination of subtle and sharp shadows that will provide an interesting texture feel for this abstract image.
Hope this helps!