In stories, the author’s point is often illustrated by showing the stark difference between two characters, objects, organizations, places, etc. The Hunger Games’ District 12 wouldn’t have been so desperate and dim if it wasn’t seen alongside the shining extravagance of the Capitol. Hogwarts was happiness personified when compared to Privet Drive. As authors, we’re almost always trying to say something. To get your point across loud and clear, consider using a bit of contrast in your setting descriptions.

Contrast can also be used to create an inner window into your character’s emotional state. Imagine a character who's in the middle of hosting an extravagant charity dinner when she discovers her husband has cheated on her. Inside, her heart is crumbling much like a fragile rock shelf unable to bear its own weight. But outside, the room is filled with color, music, and smiling faces. She’s responsible for the evening and cannot break down, even though every fiber of her wants to. Her struggle, highlighted through this contrast, is not only compelling and meaningful, it also reveals her inner strength to readers, encouraging admiration and empathy to form. 

Contrast can also be useful when you need to be a little more straightforward, such as when you're trying to describe a large-scale setting. Nature and landforms—particularly huge ones such as swamps, forests, and oceans—can be difficult to describe well because of their scale. They’re just so big; the size is hard to articulate. To adequately describe their immensity, it’s best to use contrast. Use something small in the foreground or nearby to provide a comparison and a sense of proportion.