To express the grim mood of the poem, which line is the most suitable replacement for the second line of this stanza?

The tower held the city in shadow
it was a very tall tower;
I ached to climb those cold, grey walls
and look upon the little people.

A. We witnessed it with joy.
B. tall as a cherry tree
C. like a somber peak capped by the clouds.
D. It stood there fair with a winding stair