When you’re describing a place, think about how the movement and actions of a character in that place can reveal what the place is like. For example, if your character has to push through a crowd, the reader sees and feels the crowd without you having to tell us the room is crowded.
Imagine that you are the last person left in the world. Write up to 400 words describing the world as you wake up in it. Think about not only sights and smells, but also what actions you must take – how can the things you do in the empty world show the reader what the world is like?