Imagination, creativity, and a command of the written language.
The room has a door on one side.
or
You walk into the room and notice the smell of burnt cinnamon in the air. To your left is a sturdy wooden door, though it is showing its age it still looks strong. You wonder if it is to keep something in, or out. The floor is littered with the leavings of a hastily eaten meal of bread and moldy cheese. There is a single flickering wooden torch in a rusty iron sconce half way up the wall that is opposite a sturdy wooden door. etc
