Extend the 'floor' of the way up the image - distort to keep in perspective.
I did this with 5 layers, all copies of the botton portion of the sourceimage.
merged layers, then with layer mask, brought cars and city scape out.
step 3 of 4
Added arch way. Layer mask to show city cleaned up the wall layer to match arch way.
step 4 of 4
I added the sunset. Used a couple of hue - saturation layers to what I think are better colors...