Both of the cityscapes, below, depict some amount of space in the scene. If you wanted to include that sense of depth in a painting of one or the other. it would be useful to vary the edge quality of the shapes.
Look for the edges that separate foreground from middle and background. Would it be better to keep them hard or soften them? Perhaps you want to keep the edge hard, but soften everything that's meant to be farther back.
Maybe you want the shadow areas to be soft and the illuminated shapes to have hard edges. How can you decide where you need hard or soft edges?
If imagining the scene with one kind of edge or another proves difficult, try making a version of the scene with no hard edges at all. It helps to wet the paper on both sides. It stays wet longer that way.
With an all-soft version in hand, you can ask where you most wish you had a hard edge. I recommend addressing your questions to the study rather than the photo, so you can make your decisions based on what the scene needs, instead of what it happens to have.
When you begin adding hard edges, keep them limited to only the two or three most important ones at first, based on the effectiveness of your illusion of space. I find it useful to imagine the scene as a stage set, with a simple foreground, middle ground, background layout.
Remember that it is not always most desirable to have the foreground in focus and the background soft-edged. When you have the information you need, make a clean and simple version of the image. Then, stand back and assess how well your choices worked.
If you work from an image other than one of these, please try to print out the source image so we can all see what you started with. Have fun.