That's because it is . These are part of sketches I am producing in preparation for something. This particular sketch is just focusing on mood, composition... it was quite a short turnaround. When I do the final piece I will be focusing on developing my own building designs. This process is called "photobashing" and it is very useful for achieving detailed and authentic results very quickly. 90% of this is photography, painted over to tie it all together. Give it a try, it's really fun and super effective!
It's easier than you think, and builds valuable knowledge about shape, form, composition and perspective. Start out by finding a photo you like, with an angle you like and then build on that. Adding, chopping and erasing as you go. At times you need to paint over things to tie them together, adding atmosphere here and there to add depth. It can take a couple of hours, so you can produce about 3-4 of these in a day.