Although we usually think of description as visual, we may also use other senses--hearing, touch, feeling, smell-- in our attempt to describe something for our readers.
Notice how student writer Stephen White uses multiple senses to describe Anasazi Indian ruins at Mesa Verde:
I awoke this morning with a sense of unexplainable anticipation gnawing away at the back of my mind, that this chilly, leaden day at Mesa Verde would bring something new . . . . They are a haunting sight, these broken houses, clustered together down in the gloom of the canyon. The silence is broken only by the rush of the wind in the trees and the trickling of a tiny stream of melting snow springing from ledge to ledge. This small, abandoned village of tiny houses seems almost as the Indians left it, reduced by the passage of nearly a thousand years to piles of rubble through which protrude broken red adobe walls surrounding ghostly jet black openings, undisturbed by modern man.
Look at your own topic. Would description help you explain your subject?