In 1961, Belgian artist René Magritte painted a pile of different colored facades on a large lawn in the open air. Only two facades are 100% visible because the rest of the facades partially overlap. Because the facades are smaller on the side and at the top, the pile gets depth. It is a strange painting, because in real life we do not encounter houses piled on top of each other on a lawn. Magritte liked to paint things that could only occur in a dream or fantasy world.
Exercise: Make up a mountain of apartment building facades in a landscape. Use one or more of these simple models if you like.
Perhaps this lesson is an unintended opportunity to try drawing real architecture, even if it is only parts of a building. For drawing architecture I do recommend a ruler. In the example I drew just one floor and then digitally stacked it.