All 3 Uses

solemn
in
Seventeenth Summer
(Auto-generated)

She nodded solemnly and padded back to her room on feather-soft feet, turning back to me with a cautious finger on her lips.†
Chpt Augu *

solemnly = with seriousness and dignity
Sometimes large families brushed past, all the children holding hands and gaping, trailing along in a line, their faces solemn with awe.†
Chpt Augu

solemn = very serious--possibly dignified
And ahead we could see the moon that had been hidden in the trees and it hung very low, yellow and solemn, as if it were too heavy for the sky.†
Chpt Augu

Definitions:

(1) (solemn)
in a very serious (and often dignified) manner
(2) (meaning too rare to warrant focus)
Less commonly, solemn can mean that something was done with great or appropriate ceremony. It can also be used to describe something as dark or undecorated.